Rutter's Child and Adolescent Psychiatry Book 2

involuntary repetitions, blocks or prolongations of sounds, syllables and words in discourse. These may be accompanied by secondary behaviors such as physical tension in the speech musculature, eye blinking or breaking of eye contact, movements of the head and limbs, and emotional reactions to the dysfluency, including anxiety and avoidance of speaking. Persistent dysfluency is estimated to affect 1% of the population (Yairi & Ambrose, 1999), although many more children produce normal dysfluencies during the preschool years. Like many speech, language and communication disorders, it appears to be strongly familial, and more boys are affected more often than girls (ratio of 1.65:1; Mansson, 2000). Campbell, Dollaghan, and Yaruss (2002) suggest referral to a speechlanguage therapist if parents report: 1 Frequent part-word dysfluencies; 2 Noticeable physical tension or struggle; 3 Any sign that the child is frustrated or concerned about talking; or 4 Concerns about any other aspect of speech and language development. The etiology of childhood stuttering appears to be multifactorial, with a significant genetic component (Yairi, Ambrose, & Cox, 1996). An international study by Suresh, Ambrose, Roe et al. (2006) suggested a complex etiology, with the strongest linkages being found when separate analyses were conducted for males (linkage to chromosome 7, LOD score 2.99) and females (linkage to chromosome 21, LOD score 4.5), and when interactions between sites on different chromosomes were considered. Stuttering has been associated with early difficulties in language formulation (Bloodstein, 2006) and atypical development of the auditory temporal cortex (Foundas, Bollich, Feldman et al., 2004). Furthermore, comorbidity with speech sound disorders is 30% (Yairi & Ambrose, 1999). Therefore, assessment of broader speech and language abilities is warranted. Approximately 75% of preschoolers will recover from dysfluency without professional involvement (Yairi & Ambrose, 1999). However, prognosis is poor for those who continue to stutter beyond the age of 7 years (Campbell, Dollaghan, & Yaruss, 2002). There is considerable debate regarding the most appropriate form of intervention. One approach, exemplified by the Michael Palin Centre for stammering in London (www.stammeringcentre.org), focuses on modifying the environment to reduce speaking pressure and working with children and families to reduce anxiety about speaking (for a full description see Rustin, Cook, Botterill, Hughes, & Kelman, 2001). An alternative approach, exemplified by the Lidcombe Programme (http://www3.fhs.usyd.edu.au/asrcwww/treatment/ lidcombe.htm), provides direct behavioral modification to reinforce fluent speech. There are few, if any, methodologically sound investigations of treatment efficacy and no studies that we are aware of that explicitly compare the two treatment approaches. However, there is some preliminary evidence that behavioral approaches are effective in reducing dysfluent speech in the preschool years (Jones, Onslow, Packman et al., 2005). Voice Disorders A voice disorder, dysphonia, should be suspected when a child speaks with abnormal pitch, loudness and/or hoarseness. These features can have profound effects on how a child is perceived by others and adversely affect socialization. Recent prevalence estimates from a population-based study suggest 6–11% of school-aged children present with dysphonia (Carding, Roulsone, Northstone, & Team, 2006). This is considerably higher than would be predicted from clinical referrals, but this probably reflects widespread lack of recognition of the problem (Boyle, 2000). Gender (male) and older siblings were the most significant risk factors in the Carding, Roulstone, Northstone et al. study. Campbell, Dollaghan, & Yaruss (2002) reported unpublished data from their own sample of 427 clinical referrals to a specialist clinic; 93% of these children had abnormal voice quality associated with laryngeal pathology. The most common pathology was vocal nodules (i.e., mechanical trauma caused by one vocal fold making excessive contact with the other). Surgical treatment is not recommended in such cases, as nodules are likely to return if damaging vocal behavior is not altered. Behavioral treatments can be effective and center on modifying the environment (i.e., reducing competing noise) and training the child to use the voice more appropriately. Prosodic Disorders Prosody may be defined as the suprasegmental properties of the speech signal that modulate and enhance its meaning (Paul, Shriberg, McSweeny et al., 2005a). Prosody includes variations in pitch, loudness, duration, rhythm, tempo and pausing, and serves a wide range of grammatical, pragmatic and affective functions. For example, variations in stress and intonation may signal the difference between a noun (con vict) and a verb (con vict), highlight elements within the sentence for attentional focus (the blue book, as opposed to the red one), and convey a speaker’s emotional state. It is frequently reported that impaired prosody is characteristic of verbal individuals with autistic spectrum disorder (ASD), although it may not be universal. Paul, Shriberg, McSweeny et al. (2005a) reported that 47% of the 30 adolescent and adult speakers with ASD they investigated had prosodic abnormalities. Such abnormalities have a negative effect on how listeners perceive social and communicative competence and pose significant obstacles to social integration and employment (Paul, Augustyn, Klin et al., 2005b). Disorders of Language and Communication Components of Language Competent adults produce language so effortlessly that it is easy to forget just what a complex system it is. All spoken languages can be studied in terms of four levels of description: phonology (speech sounds); semantics (meaning); grammar (formal ways of using word order and inflection); and SPEECH AND LANGUAGE DISORDERS 787 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 787

pragmatics (use of language to communicate). However, there is considerable variation from one language to another at all of these levels. For instance, Chinese does not have word inflections, whereas Turkish has numerous inflections that are appended to word stems in an agglutinative fashion. Clearly, the task confronting the young language learner is going to be very different in these two languages, and in English, which uses inflections, but much more sparsely than many other languages. As well as the different levels of linguistic representation, language can be divided into expressive (production) and receptive (comprehension) aspects. To be a competent communicator, the child must learn to recognize and produce the distinctive speech sounds in the language (the phonology), establish a “mental lexicon” containing representations of words as phoneme sequences linked to meanings, master the grammatical structure of the ambient language, and learn how to select a message to convey meanings economically and effectively to others (pragmatics). Furthermore, language processing has to be carried out at speed. Differential Diagnosis of Specific Language Impairment When a child presents with language impairment, the clinician needs to establish whether there is any causal factor present that could explain the language difficulty, or whether the language impairment is part of a recognized syndrome. The majority of cases of language impairment in children have no obvious cause (Shevell, Majnemer, Rosenbaum, & Abrhamowicz, 2000), and occur in the context of otherwise normal development. This is known as specific language impairment (SLI) and also as primary language impairment, developmental language disorder or developmental dysphasia. Before considering the characteristics of SLI we briefly discuss other conditions that need to be considered when making a differential diagnosis. Low Non-verbal Ability An early step in the assessment of a language-impaired child is administration of a non-verbal IQ test. Cases of intellectual disability (non-verbal IQ more than 2 SD below average) are usually straightforward enough to identify (see chapter 49). However, there are many children with slow language development who do not have a syndrome of intellectual disability, but nevertheless have below-average non-verbal IQ. Traditional definitions of SLI usually require that non-verbal IQ is broadly within normal limits. More stringent definitions also require that there should be a significant mismatch between language ability and non-verbal IQ (equivalent to 1 SD in ICD10). However, there is increasing disquiet about the use of IQ discrepancy criteria, because these exclude large numbers of children who are not intellectually impaired and yet have evident language difficulties. For instance, if we require there to be a 1 SD difference between a language and non-verbal index, then we would exclude a child with a language level 2 SD below the mean and a non-verbal score 1.3 SD below the mean. This child would not meet criteria for intellectual disability and so would be left in a diagnostic limbo and may be denied access to intervention, even though the profile and severity of language difficulty may be similar to those seen in a child who does meet the discrepancy criterion (Tomblin & Zhang, 1999). Furthermore, twin studies suggest the same genetic risk factors operate for children with language difficulties regardless of their non-verbal IQ (Bishop, 1994). Thus, the logic of distinguishing between children who do and do not meet strict IQ discrepancy criteria is questionable. Auditory Problems Hearing should always be assessed by an audiologist in a child who presents with language impairment. As neonatal screening programs become more widespread, it is unusual to find an undetected sensorineural hearing loss in a languageimpaired child, but one needs to be alert to the possibility of screening errors or a progressive hearing loss. Hearing loss restricted to a specific frequency range is easy to miss, because the child appears responsive to sound, yet crucial information may be lost from the speech signal, leading to a profile of impaired language development that may look similar to SLI (Stelmachowicz, Pittman, Hoover, Lewis, & Moeller, 2004). It is much more common to find conductive losses in young children with language impairments. However, it is not easy to know how to interpret these. Early studies suggested unusually high rates of language and literacy problems in children who had otitis media with effusion (OME; Holm & Kunze, 1969). OME typically causes a conductive loss of up to 40 dB, and it seems plausible that such a loss might assume significance in a child in the early stages of language learning. However, more recent epidemiological studies have questioned whether OME is a major etiological factor in language impairment (Feldman, Dollaghan, Campbell et al., 2003). A substantial number of children under 5 years of age have undetected and asymptomatic middle ear disease, particularly in the winter months. Prospective studies of children with and without prolonged episodes of OME have found little or no impact on verbal skills, suggesting that language development is resilient in the face of the mild associated hearing losses. OME may assume more importance if it is chronic and persistent (Feldman, Dollaghan, Campbell et al., 2003). However, we would recommend caution in assuming that OME is the main causal factor if it is detected in a child with language impairment. There is a large body of knowledge on assessment of the integrity of the peripheral auditory pathways in children, but much less agreement concerning diagnosis of central auditory processing deficits. In some countries, notably the USA and Australia, the diagnosis of auditory processing disorder (APD – sometimes prefixed with C for central) is frequently made. However, it is far less common in the UK. The principal difficulty with the APD concept is that it is typically diagnosed using tests that use verbal materials (e.g., listening to speech in noise) or being presented with two streams of speech in different ears (Moore, 2006). These tests have demonstrated CHAPTER 47 788 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 788

validity when used to identify central auditory lesions in adults with acquired brain damage, who can be assumed to have normal language abilities. However, their interpretation is complicated in children, because it is difficult to distinguish poor performance resulting from a primary language problem from a genuine auditory difficulty (Rosen, 2005). To illustrate this point, consider how you would fare if you were asked to carry out a range of listening tests presented in a language with which you had limited competence. It is likely that under optimal listening conditions you would do much better than when words were presented in noise or in a competing speech situation. This is because a competent speaker of a language does not simply decode speech by bottom-up analysis of the speech signal; he or she also employs top-down processing to predict and fill in information. If one uses speech-based tests in diagnosis, then one is likely to end up finding numerous cases of language impairment that appear to be caused by APD, but where the problem may in fact arise for quite different reasons. In our experience, many children who receive a diagnosis of APD from an audiologist would be given a diagnosis of SLI, dyslexia, attention deficit/hyperactivity disorder (ADHD) or autistic disorder if seen by a speech and language therapist, psychologist or child psychiatrist. In emphasizing these assessment difficulties, we do not wish to imply that APD is not a valid category; it is plausible that some children have immature or dysfunctional development of the central auditory pathways and this might well impact on language development. However, our concern is that APD is often diagnosed using instruments of questionable validity, leading to implementation of auditory-based interventions that may not be justified. It is vital to adopt an interdisciplinary approach, whereby audiologists work together with other professionals to ensure that children receive appropriate diagnoses and intervention. It is hoped that as research on APD advances, better assessment methods, using more objective electrophysiological as well as non-verbal behavioral tests (Liasis, Bamiou, Campbell et al., 2003) will give a clearer picture. Acquired Epileptic Aphasia Acquired epileptic aphasia (AEA), also known as Landau– Kleffner syndrome, is a rare cause of childhood language impairment which is often misdiagnosed. The typical presentation is one of deterioration in language skills in the preschool years after a period of normal development. Because the child previously spoke normally, the disorder may be misdiagnosed as selective mutism (see p. 791); however, in AEA, there is genuine loss of language skills, with comprehension problems predominating. Deafness is usually suspected but ruled out on the basis of a hearing test. Many children with AEA have relatively selective problems with language in the context of preserved non-verbal ability, but in some children there are associated behavioral disturbances, which further complicate the diagnosis (Deonna & Roulet-Perez, 2005). The epileptic manifestations of AEA are not obvious, because overt seizures are uncommon, and it may be necessary to carry out a sleep electroencephalogram (EEG) to demonstrate EEG abnormalities. These can be marked, and there has been debate as to how far this disorder overlaps with slow wave status epilepticus in sleep (SWSS). Some children, particularly those with onset after 6 years of age, can make a good recovery, but the prognosis for those with preschool onset is often poor and substantial receptive language deficits may persist to adulthood. Our recommendation is that any child with language regression accompanied by comprehension problems should be referred to a pediatric neurologist for an evaluation of AEA. Deonna and Roulet-Perez (2005) note that pharmacological interventions can be effective, but there is wide variation in responsiveness to treatment, and in the absence of controlled clinical trials it is difficult to give precise guidelines. Deonna (2000) recommended that when receptive language difficulties persist for more than a few weeks or months, it is crucial to provide the child with an alternative mode of communication. Sign language can be effective and does not interfere with attempts to retrain comprehension of auditory language (Roulet-Perez, Davidoff, Prélaz et al., 2001). Delayed Language Development: Late-Talkers When diagnosing SLI, it is important to determine when a young child’s language delay represents a significant departure from normal variation, which can be difficult when the child is younger than 3 years old. Late-talkers are identified as having severely restricted vocabulary at age 2 years (fewer than 50 words). It is unclear how many late-talkers have similarly impaired receptive language skills, because many studies include only children with normal comprehension (Rescorla, 2005). Many late-talkers meet typical exclusionary criteria for SLI such as normal non-verbal ability and no hearing loss; however, most late-talking 2-year-olds will normalize language function by the time they enter school (Rescorla, 2005), whereas the long-term prognosis for school-aged children with SLI is less optimistic (Stothard, Snowling, Bishop et al., 1998). Dale, Price, Bishop, and Plomin (2003) followed a large sample of twins from 2 to 4 years of age. Late-talkers were identified as those 2-year-olds with expressive vocabulary scores in the bottom 10th centile (15 words or fewer on a modified version of the MacArthur Communicative Development Inventory). By age 4, 60% had age-appropriate scores on parent-report measures of vocabulary, grammar and use of abstract language. It appears that gains in language skill are maintained over time. Paul (2000) reported that 84% of late-talkers in her cohort had language scores within the normal range at age 7. Rescorla (2005) followed 28 late-talkers from preschool to age 13 and found that, at this age, all of the children scored within the normal range on standard measures of language and literacy. However, their scores were significantly lower than a comparison group of typically developing children matched for socioeconomic status (cf. Stothard, Snowling, Bishop et al., 1998). Rescorla argued that late-talkers represent a subgroup of SLI characterized by less severe language weakness. 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Although 60–85% of late-talking children will improve without direct intervention, a minority will not (Paul, 2000; Dale, Price, Bishop et al., 2003). It is not currently possible to distinguish reliably between those children with transient and persistent impairments. Dale, Price, Bishop et al. (2003) found that severity of language delay at age 2 did not predict language status at age 4. In addition, neither gender nor level of maternal education significantly predicted group outcome. Paul (2000) reported that children with persistent language difficulties tended to have lower non-verbal abilities, although scores on non-verbal assessments were still within the normal range and there was considerable overlap between groups with good and poor outcome. In addition, high socioeconomic status and prosocial adaptive communicative behaviors were associated with good outcome at age 7. A much smaller-scale study by Thal, Tobias, and Morrison (1991) indicated that poor receptive language skills and failure to use gesture were associated with persisting language difficulties. Given these findings, a dilemma facing practitioners is what to do when language delay is identified during the preschool years. Conventional wisdom posits that early intervention is desirable, but Paul (2000) questioned the ethics of treating children who are otherwise developing normally, have normal language comprehension and do not present with any additional risk factors for a language “disorder” that they may overcome naturally without any professional help. Instead, she advocates initial parent training to optimize language input in conjunction with careful monitoring of language development. Even though good language outcomes are often seen in latetalkers, there is evidence to suggest they should be monitored because such children may be at risk for other developmental difficulties. In a survey of over 1000 children, Horwitz, Irwin, Briggs-Gowan et al. (2003) found that late-talkers tended to show poor social interaction, which was in turn associated with an increased risk of emotional and behavioral disorders. Furthermore, it would seem prudent to give the child support in the early stages of reading and writing, given a suggestion that there is a risk of weak literacy skills in children who were late-talkers (Rescorla, 2005). Autism and Pragmatic Language Impairments Delayed language development and poor communication skills are hallmarks of autistic disorder, and the issue of differential diagnosis between autistic disorder and specific developmental language disorder frequently crops up in the clinical setting. Diagnosis of autistic disorder is covered in detail in chapter 46, so in this chapter we focus on areas of diagnostic difficulty. Autistic disorder should be considered when the child’s language difficulties are accompanied by more pervasive difficulties affecting social interaction, non-verbal communication and play, or if the child shows unusual repetitive or ritualistic behaviors or restricted interests. The clinician needs to consider whether language development is merely delayed, or whether there are deviant features that would not be regarded as normal at any age, such as repetitive use of stereotyped catchphrases, unusual and exaggerated intonation, pronoun reversal or a frequent failure to respond when the parent attempts to attract the child’s attention. Some higher-functioning children with autistic disorder (i.e., those children with non-verbal IQs within the normal range) resemble our illustrative child Jack in having superficially complex language; they may appear verbose and achieve ageappropriate scores on tests of expressive language or simple vocabulary measures. However, such measures may overestimate true language ability (Mottron, 2004) and the same children usually have significant comprehension deficits in less structured and more naturalistic discourse settings (Adams, Green, Gilchrist, & Cox, 2002). Textbook cases of autistic disorder and SLI are relatively easy to differentiate, but many children present with a pattern of symptoms that does not fit unambiguously in either category, while showing some features of both. Thus, their difficulties extend beyond the characteristic grammatical deficits seen in SLI, but they do not have the full triad of impairments in severe enough form to warrant a diagnosis of autism. Differentiation between the two disorders may be hampered by a changing clinical picture over time (Charman, Taylor, Drew et al., 2005; Mawhood, Howlin, & Rutter, 2000). Conti-Ramsden, Simkin, and Botting (2006) applied standard diagnostic instruments (Autism Diagnostic Interview – Revised; Lord, Rutter, & Le Couteur, 1994; Autism Diagnostic Observation Schedule – Generic; Lord, Risi, Lambrecht et al., 2000) to 76 adolescents with a history of SLI, none of whom had been regarded as autistic in middle childhood. The majority of individuals did not meet criteria on either measure, but 3.9% met criteria for autistic disorder on both assessments, a prevalence rate more than three times greater than would be expected from the general population (Baird, Simonoff, Pickles et al., 2006). A further 26% met criteria on one or other measure but not both. Similar results were obtained by Bishop and Norbury (2002), who noted that many children with language impairment displayed difficulties with broader aspects of communication and social interaction, although restricted interests and rigid behaviors were less characteristic of this population. In cases where a child meets criteria in one or two domains of the autistic triad or exhibits subthreshold symptomatology across domains, a diagnosis of “pervasive developmental disorder not otherwise specified” or “atypical autism” is frequently applied. However, there is concern that these terms may be overused, and do not provide helpful information about symptom profile, nor do they facilitate decisions about educational placement. Bishop (2000) suggested that the term “pragmatic language impairment” (formerly “semantic-pragmatic disorder”) might be useful for describing children who do not meet full diagnostic criteria for autistic disorder, but whose language difficulties affect social interaction and the use of language in context. The use of this term was not intended to imply a new and discrete disorder; rather, “pragmatic language impairment” is seen as a variable correlate of both SLI and milder forms of autistic spectrum disorder (Norbury, Nash, Bishop, & Baird, 2004). 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In reality, the diagnostic label chosen may reflect the practitioner’s theoretical stance and the practical implications a particular diagnosis brings with regard to accessing appropriate educational and remedial provision. The important point to recognize is that rather than attempting to draw a discrete diagnostic line between SLI and autistic disorder, it is more helpful to think in terms of multidimensional space, with children varying in terms of the severity of impairments in language, social interaction and range of interests. Selective Mutism Occasionally, the clinician will encounter a child who is extremely reticent in the clinic setting. In these instances, it is important to establish that the child does speak with others in more familiar situations such as school and home. However, if the child’s communication varies significantly in different settings, the practitioner should consider the possibility of selective mutism. Selective mutism (SM) is diagnosed in the child who consistently does not speak in certain situations in which there is an expectation for speaking (e.g., school), but can and does speak normally in some situations (e.g., at home; Steinhausen, Wachter, Laimbock et al., 2006). The disorder was previously known as “elective” mutism, but the terminology has been revised to avoid implying that children are being obstinate or oppositional when they remain silent (Cline & Baldwin, 2004; Cohan, Chavira, & Stein, 2006a). DSM-IV-TR (American Psychiatric Association, 2000) and ICD–10 (World Health Organization, 1996) criteria stipulate that in order to receive a diagnosis, the mutism must persist for more than 1 month (not including the first month of school), and cannot be accounted for by a communication disorder or a lack of familiarity with the ambient language of the social situation. Toppelberg, Tabors, Coggins, Lum, and Burger (2005) further recommend that bilingual children are not diagnosed with SM unless the mutism persists for longer than 6 months and is apparent in both languages. Prevalence estimates vary depending on the criteria used and the population studied, with higher rates of transient mutism associated with starting school. Cline and Baldwin (2004) estimate 6–8 cases of selective mutism per 1000 throughout childhood, with a preponderance of girls (55–65% of cases), consistent with the results of recent community studies, which have found rates of approximately 75% (Cohan, Chavira, & Stein, 2006a). The precise cause(s) of SM is unknown; although trauma may precipitate mutism, it is not implicated in the majority of cases (Steinhausen & Juzi, 1996). SM is generally regarded as a variant of anxiety disorder (Steinhausen, Wachter, Laimbock et al., 2006; Vecchio & Kearney, 2005), rather than being categorized with speech and language disorders. Rates of comorbid anxiety and phobic disorders are high, both in affected children and their first-degree relatives, and some success in treatment has been reported using drugs that effectively reduce anxiety (for a review see Cline & Baldwin, 2004). However, it would be wrong to imply that social anxiety is the only problem; other factors are also often implicated, including bilingualism and speech and language impairment, suggesting that self-consciousness about inadequate communication plays a part in maintaining the disorder (Manassis, Fung, Tannock et al., 2003). The consensus of opinion is that SM is the culmination of multiple predisposing, precipitating and perpetuating factors (Cohan, Price, & Stein, 2006b; Johnson & Wintgens, 2001). Assessment of the child with SM may be particularly challenging, as the assessment process itself might further increase anxiety and reluctance to speak. At first meeting, it is most important to create a relaxed atmosphere in which the child feels little pressure to communicate with an unfamiliar adult. In this session, the clinician may take a detailed case history from the parents, focusing on where, when and with whom the child does speak and obtaining detailed examples of how the child communicates in different settings. During conversation with the parents, the clinician may unobtrusively observe the child playing and, if possible, interacting with parents or siblings. Direct assessment of expressive language may not be possible at this point, although many children with SM will cooperate with receptive language testing if this just involves carrying out commands or pointing to pictures, and this can give valuable information about general language level (Manassis, Fung, Tannock et al., 2003). Formal assessment may be supplemented by asking parents to record the child’s language skills in a more comfortable arena, perhaps telling a story at home, or keep a diary of what the child says and the contexts in which language occurs. Johnson and Wintgens (2001) provide further examples of techniques for gaining the child’s confidence to enable assessment to proceed. The most successful treatments are thought to combine behavioral and psychopharmacological interventions, but there appears to be no systematic research on the efficacy of this approach (Cline & Baldwin, 2004). Cohan, Chavira, & Stein (2006a) conducted a critical review of psychosocial treatments published over a 15-year period. The techniques used in these studies included positive reinforcement for speaking to classmates, systematic desensitization to anxiety-provoking situations, language training, family therapy and self-modeling techniques, in which the child with SM listens to recordings of him or herself speaking in situations in which he or she is usually mute. Although the majority of these studies report increases in speaking behavior, the findings are limited by very small participant numbers and a lack of suitable control groups. A recent longitudinal study demonstrated considerable improvement in symptoms of SM over time, but rates of psychiatric disorder, especially social phobia, remained high (Steinhausen, Wachter, Laimbock et al., 2006). Prognosis is especially poor when a family history of SM is present. Assessment of Language and Communication Approximately 50% of children referred for psychiatric evaluation have clinically significant language impairments that SPEECH AND LANGUAGE DISORDERS 791 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 791

are frequently unsuspected (Cohen, 2001). In many clinical contexts it is not possible to offer the time and expertise necessary for every referral to receive an in-depth assessment of language. However, it can be informative to gain an overview of the child’s language development and current communicative functioning by taking a detailed case history and asking caregivers to complete a screening checklist. The Children’s Communication Checklist-2 (CCC-2; Bishop, 2003a) is a 70-item checklist for children aged 4 years and over that asks parents to rate the frequency of communicative behaviors in everyday situations, thus providing a naturalistic assessment of functioning. One advantage of this assessment is that it covers both structural aspects of language (phonology and syntax) as well as pragmatic aspects of communication, which are more difficult to measure on face-to-face assessment. The CCC-2 reliably distinguishes children with communication impairment from typically developing children (Norbury, Nash, Bishop et al., 2004) and an earlier version of the checklist identified children at genetic risk for language impairment as effectively as standardized tests (Bishop, Laws, Adams, & Norbury, 2006b). However, it should be noted that CCC-2 is not suitable for children who are not yet speaking in sentences. More detailed evaluation of language and communicative functioning will typically be undertaken by a speech-language therapist or specialist psychologist. A number of standardized assessments tapping all domains of language are available in English, but this is not necessarily so in other languages. The application of English language assessments to children from non-English speaking backgrounds is not recommended, as test scores may not accurately reflect the child’s competence in his or her native language. There is evidence that “knowledge-dependent” measures, such as vocabulary tests, exaggerate cultural and socioeconomic differences between children, whereas “processing” measures that vary difficulty by manipulating the amount of material that has to be processed (e.g., nonsense word repetition), provide a culturally unbiased estimate of language ability (Campbell, Dollaghan, Needleman, & Janosky, 1997). Table 47.1 provides a list of commonly used language assessments in the UK, including the domain of language targeted and the age range appropriate for testing. There is currently no clear consensus on what degree of impairment on standardized assessment constitutes a significant difficulty. A score of –1 SD (equivalent to 16th centile) on a single assessment may not interfere with the child’s educational or social development, whereas consistently low scores across a number of language domains or an extremely low score on one measure (–2 SD or 3rd centile) may be more problematic. Tomblin, Records, and Zhang (1996) used a battery of language tests covering different aspects of receptive and expressive processing, and combined these into five composites: expressive language, comprehension, vocabulary, grammar and narrative. SLI was diagnosed if two or more of these composites fell more than 1.25 SD below age level (10th centile), non-verbal IQ was 87 or more, and no exclusionary conditions were present. In a population sample, this resulted in 0.85 sensitivity (identifying true cases of impairment) and 0.99 specificity (correctly identifying unimpaired cases). Note that the definition of SLI used by Tomblin et al. was considerably less stringent than that of ICD-10 (World Health Organization, 1996), which requires that language test scores must be 2 SD or more below age level. Application of this criterion would give a lower prevalence rate. In DSM-IV-TR (American Psychiatric Association, 2000) a distinction is drawn between expressive vs. mixed receptiveexpressive subtypes of language disorder. The importance of establishing the level of receptive language should not be underestimated: poor comprehension is an important predictor of outcome in a language-impaired child (Stothard, Snowling, Bishop et al., 1998). However, if strictly interpreted, the DSM-IV system is unworkable. This is because it defines Expressive Language Disorder as having an expressive language score that is “substantially below” both non-verbal IQ and receptive language, whereas in Mixed Receptive-Expressive Language Disorder, both expressive and receptive language are “substantially below” non-verbal IQ. This creates a problem of how to categorize a child with average non-verbal IQ and a mild receptive language impairment and a more severe expressive impairment (e.g., receptive language score is 0.8 SD below average and expressive language score is 1.2 SD below average). If we interpret “substantially below” in terms of a 1-SD discrepancy, such a child would not meet criteria for either DSM subtype. Furthermore, the distinction between the two subtypes seems artificial; both genetic and developmental data suggest that they correspond to points on a continuum of severity (Bishop, North, & Donlan, 1995). Prevalence, Causes and Correlates of Specific Language Impairment Research on SLI is complicated by the variety of diagnostic criteria that have been employed. It is rather unusual to find research that focuses on “pure” SLI in which there is a substantial discrepancy with non-verbal IQ. More commonly, an IQ cut-off is used to establish that children are within broadly normal limits. In addition, as noted in chapter 3, SLI is often accompanied by other neurodevelopmental disorders: rates of co-occurrence of ADHD, developmental coordination disorder and academic difficulties are all high. Studies vary in how far they explicitly include or exclude children with these comorbid conditions, with speech problems or with autistic features. It is likely that estimates of prevalence, comorbidity and etiology will depend on the phenotype that is studied. Prevalence The most frequently cited prevalence figure for SLI comes from an epidemiological study by Tomblin, Records, Buckwalter et al. (1997), who estimated that 7.4% (95% confidence interval [CI] 6.3–8.5%) of 5- to 6-year-old children in an Iowa sample met diagnostic criteria as defined above. Intriguingly, of those who did meet criteria for SLI, only 29% had previously been identified as having language difficulties. If the CHAPTER 47 792 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 792

criteria were made more stringent, to include only those with composite language scores more than 2 SD below average, it was still the case that only a minority of affected children (39%) had been identified clinically. This result suggests that the features that lead to a child being identified as having an SLI are different from those that are picked up by standardized tests (Bishop, Laws, Adams et al., 2006b). In general, teachers and parents will notice a child whose speech is unclear or whose language structure is so immature as to sound ungrammatical, but poor verbal memory, limited understanding, weak vocabulary and lack of complex grammar are easier to miss. As with many other neurodevelopmental disorders, more males than females are affected with SLI, although the male preponderance was far less in the epidemiological study of Tomblin, Records, Buckwalter et al. (1997), who reported 1.33:1 boys to girls, than in samples recruited from clinical sources (e.g., Robinson, 1991, reported a ratio of 3.8:1). There is no evidence that different genetic influences are implicated in causing language impairment in males and females; a comparison of same-sex and opposite-sex twin pairs found a similar magnitude of genetic and environmental influences in both sexes (Viding, Spinath, Price et al., 2004). As Tomblin, Records, Buckwalter et al. (1997) pointed out, there is an intrinsic difficulty in attempting to compare prevalence in different racial groups, because even if the core language is the same across races, there are likely to be cultural differences in language use that will lead to biased test results. Campbell, Dollaghan, Needleman et al. (1997) suggested such bias could be eliminated by avoiding language tests that were affected by prior knowledge or experience, but we are not aware of any epidemiological studies that used such measures to compare different rates of SLI in different races or cultures. Correlates of SLI Although SLI is “specific” insofar as the language disorder is not accompanied by low non-verbal ability, there are frequently accompanying impairments in other aspects of functioning. Literacy problems are found in most but not all children with SLI. The question of what characterizes those children who learn to read and write despite SLI is intriguing but as yet not fully understood; however, poor phonological processing appears a key factor (Bishop & Snowling, 2004; Catts, Adlof, Hogan, & Weismer, 2005). Another frequent accompaniment to SLI is motor impairment, which may not be evident in everyday interactions, but becomes so on formal testing (Hill, 2001; Webster, Majnemer, Platt, & Shevell, 2005). Comorbidity with Psychiatric Disorder Early research by Cantwell and Baker (1991) demonstrated a high rate of psychiatric disorder, including but not limited to ADHD, in children referred for speech and language disorders. In one of the few epidemiological studies to address this issue, the Ottowa Longitudinal Study, it was found that language impairment in 5-year-olds was one of the strongest predictors of psychiatric outcome at 12 years of age, even after measures of social background were taken into account (for review see Beitchman, Brownlie, & Wilson, 1996). In this study, ADHD and emotional disorders were the most common psychiatric diagnoses. A series of studies by Cohen, Hodson, O’Hare et al. demonstrated that the converse also applied. Of children referred for psychiatric assessment solely for socioemotional disturbances, 33% were found to have previously undiagnosed language impairment. When combined with those whose language impairments had already been identified, some 50% of school-aged children referred to out-patient mental health clinics had clinically significant language impairments (for review see Cohen, 2001). Such co-occurrences raise a host of questions about causation. An obvious possibility is that inability to express one’s needs and ideas leads to a sense of frustration and impotence, and subsequent acting-out behavior. However, if this were the principal route to psychiatric disorder, we would expect the greatest evidence of psychopathology to be seen in children with expressive difficulties, whereas most studies find receptive language difficulties pose substantially greater risk. Failure to comprehend language can lead to inappropriate accusations in the classroom of laziness, willfulness or inattention, and it will also limit the opportunities to form close relationships that would normally exert a protective effect. Redmond and Rice (1998) contrasted this latter type of “social adaptation” account with a “social deviance” model that regards both behavior and language problems as indicators of an underlying trait of disturbed psychosocial development. They argued that parent and teacher ratings of socioemotional status in children with SLI showed little congruence or temporal stability, supporting the idea that behavioral problems were consequences of specific communicative experiences rather than reflecting intrinsic deficits in the child. However, rates of behavior disorder were relatively low in their sample, and the possibility remains that more severely affected children have socioemotional deficits that go beyond what could be reasonably regarded as adaptations to poor communication (see also Bishop, 2000). Another route from language impairment to psychiatric disorder is through the experience of school failure. Both Beitchman, Brownlie, & Wilson (1996) and Tomblin, Zhang, Buckwalter, and Catts (2000) found that the risk of psychiatric disorder was substantially raised in those children whose language impairment was accompanied by reading disability, and was much lower in those who were experiencing academic success. In both these studies, this association was less evident when the same children’s behavior problems were assessed before they learned to read; this suggests that it is experience of school failure that exacerbates psychiatric risk. One further mechanism whereby language could affect psychiatric status is through its role in inner speech and selfregulation. Language is a tool for thought as well as a means of communication, and it affects how we structure our experiences, plan for the future and reflect on the past. A child with limited language understanding is anchored more firmly in the here and now, and may find it hard to delay gratification, think SPEECH AND LANGUAGE DISORDERS 793 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 793

through another person’s motivations or appreciate chains of causality. In the case of autistic disorder, verbal ability is strongly linked to the development of understanding of other minds, which is thought to mediate social understanding and interaction (Happé, 1995), and those children with significantly lower verbal ability in relation to non-verbal ability demonstrate the most severe deficits in social interaction (Joseph, Tager-Flusberg, & Lord, 2002). We need more research relating specific aspects of language skill to cognitive processes and behavioral outcomes in SLI to evaluate the plausibility of different causal pathways to disorder, compared with other accounts such as one that would regard language impairment and psychiatric disorder as independent consequences of some third factor such as poor parenting or social disadvantage. In addition, we need research on how best to help children whose psychiatric problems are associated with language difficulties. The role of language in thinking has implications for intervention: some children have language problems that could make it difficult to use methods such as cognitive–behavioral therapy. For instance, if the child does not understand what is meant by “if . . . then”, and has difficulty thinking about events beyond the here and now, then it may be counterproductive to try to use social problem-solving approaches that involve thinking about solutions to hypothetical situations. Genetic Factors Twin studies have converged in finding that SLI is a highly heritable disorder (for review see Bishop, 2001). In 1990, excitement was generated by the discovery of a three-generation family, the K.E. family, in which a speech and language disorder appeared to be inherited in an autosomal dominant fashion. The earliest account of this family focused on their verbal dyspraxia (Hurst, Baraitser, Auger et al., 1990), but subsequent reports have drawn attention to coexisting problems with broader oral language skills (Watkins, Dronkers, & Vargha-Khadem, 2002). The mutation responsible for the disorder has since been identified as affecting the function of a transcription factor, the FOXP2 gene, which influences the development of the brain as well as other organs (for an overview see Fisher, 2005). Although other cases of speech and language impairment linked to FOXP2 have been reported (Feuk, Kalervo, Lipsanen-Nyman et al., 2006; Macdermot, Bonora, Sykes et al., 2005), it is evident that this is a rare mutation that cannot account for the majority of cases of SLI. Although it is possible that other single major genes may be involved in the etiology of some cases of SLI (Bishop, 2005), it is likely that for many children the etiology will involve the combined influence of several genes and environmental factors, each of small effect. Research on the genetics of SLI is moving ahead on three fronts. First, there are molecular studies that have made progress in identifying linkages to sites on chromosomes 3, 16 and 19 (Newbury & Monaco, in press). Second, there are behavioral genetic studies that attempt to refine the phenotype of heritable SLI. In general, these suggest that we will make better progress in molecular genetic studies if we abandon the conventional clinical criteria for SLI and move instead to define the phenotype in terms of measures of underlying cognitive and linguistic processes (Bishop, 2006). One important clinical message to emerge from genetic studies is that genes can increase a child’s risk of SLI, but they do not act in a deterministic fashion. Whether or not a genetic risk is manifest as a language disorder may depend on environmental factors (Bishop, 2001). Finally, there is a recognition that we need to move away from focusing on individual neurodevelopmental disorders, to consider whether there are genetic risks for SLI that also affect related conditions such as developmental dyslexia or autistic disorder. In the case of dyslexia, it is clear that there are some genetic variants that increase the risk for both SLI and reading problems but, nevertheless, there is little overlap in the sites of significant linkage found in whole-genome scans for these two conditions (Fisher, 2006). There has been considerable interest in the idea that a common genetic locus might be found that increases the risk for both SLI and autism (Folstein & Mankoski, 2000), but this has yet to be validated, and behavioral studies suggest that phenotypic similarities between the two disorders may be only superficial (Bishop, Maybery, Wong et al., 2004; Whitehouse, Barry, & Bishop, 2007). Environmental Factors There is little evidence that environmental factors alone are sufficient to cause the selective deficits in grammar and phonology that characterize SLI. However, environmental factors may be implicated in early language delay and can have a role in mediating the developmental course of language disorders and the impact of language impairment on the child’s well-being. Family socioeconomic status (SES) has long been associated with child language development, with children from lower SES environments experiencing protracted rates of language development in relation to peers from more affluent homes. It is suggested that the relationship between SES and language impairment is mediated by maternal education, via the quantity and quality of mothers’ communicative interactions with their children (Hoff & Tian, 2005). However, other studies have found that SES (as measured by income or maternal education) is not a reliable predictor of long-term language impairment (Dale, Price, Bishop et al., 2003; Paul, 2000). Furthermore, even when SES is implicated in language or literacy impairment, one must consider that environments are at least partially genetically influenced (Oliver, Dale, & Plomin, 2005). In other words, a mother may have a limited educational experience and poor career prospects because of her own language limitations. Nevertheless, early language delay in the presence of low SES should alert the clinician of the need to monitor linguistic progress carefully. In a multicultural society, one must establish whether a child is presenting with a language disorder or a language difference. Two questions must be addressed: 1 Is the child impaired only in his or her ability to learn the ambient language, or are language impairments evident in the child’s home language as well? CHAPTER 47 794 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 794

2 If the child does have language impairment, does exposure to more than one language exacerbate the child’s language learning difficulties? Studies of SLI in bilingual language learners are in their infancy, and there is a dearth of longitudinal data with which to answer these important questions. For some languages, such as Spanish in the USA, there now exists a range of culturally appropriate, well-standardized assessments with which to assess bilingual children, but the situation is far less satisfactory for many other language communities. It is not safe to assume that a straightforward translation of an English test into the child’s home language will provide an accurate picture of the child’s language ability. In these instances, it will be important to obtain a picture of the child’s communicative competence from the primary caregiver. It may be particularly beneficial to ascertain whether the caregiver is concerned about the child’s communication and how this child’s development compares with other children in the family or community. The limited research available suggests that experience with two or more languages does not cause or compound SLI (Paradis, Crago, Genesee, & Rice, 2003). Thus, most speechlanguage clinicians recommend that families continue to provide rich input in the child’s home language and that, where possible, intervention should target both languages. However, there is a no systematic research comparing monolingual vs. bilingual therapy in such cases, and it could be argued that the child with SLI may be particularly handicapped by the challenge of mastering two or more languages simultaneously. One recent study by Cheuk, Wong, and Leung (2005) endorsed this view, but focused on preschool children; thus, it is likely that many would achieve normal language outcomes. Longitudinal studies of bilingual children with SLI are clearly needed. Neurobiology Most children with SLI show no gross abnormalities of the brain on structural imaging. More fine-grained analyses have revealed evidence for four kinds of developmental brain anomaly associated with SLI: 1 Abnormalities in the organization of different kinds of brain cell (ectopias and microgyri; Galaburda, Sherman, Rosen, Aboitiz, & Geschwind, 1985); 2 Additional gyri in frontal or temporal regions (Clark & Plante, 1998; Plante & Jackson, 1997); 3 Unusual proportions of different brain regions (Herbert, Ziegler, Makris et al., 2003; Jernigan, Hesselink, Sowell, & Tallal, 1991; Leonard, Lombardino, Walsh et al., 2002); and 4 Anomalous cerebral lateralization (De Fossé, Hodge, Makris et al., 2004; Gauger, Lombardino, & Leonard, 1997; Herbert, Ziegler, Makris et al., 2003). However, the field is plagued by inconsistent findings: for instance, whereas SLI was associated with small cerebral volume in studies by Jernigan, Hesselink, Sowell et al. (1991) and Leonard, Lombardino, Walsh et al. (2002), it was associated with large cerebral volume in the study by Herbert, Ziegler, Makris et al. (2003). Leonard (1997) noted that such associations as are found are weak and probabilistic, and abnormalities that are more frequent in SLI than in typically developing children may also be seen in other disorders. In her own research, she has had some success in showing clearer relationships between disorder and brain anomaly by distinguishing between cases with language comprehension impairments and those with more restricted phonological deficits (Leonard, Lombardino, Walsh et al., 2002, Leonard, Eckert, Given et al., 2006). Overall, the picture from structural brain imaging has been confusing and contradictory. The one thing we can conclude is that such anomalies as are found in SLI appear to arise early in neurodevelopment, rather than being brought about by early acquired lesions. This fits with the view of SLI as a disorder in which genetic influences lead to a brain that is wired up in a non-optimal fashion. From a clinical perspective, it is unlikely that brain imaging will provide information of diagnostic or prognostic utility in a child with SLI (Shevell, Majnemer, Rosenbaum et al., 2000). Few functional imaging studies have been conducted with SLI, and those that have been performed are difficult to interpret. Thus, if one shows underactivation of regions implicated in language processing, it is unclear if this is cause or consequence of the language disorder. Functional imaging can nevertheless be useful in providing evidence for unusual localization of specific functions (e.g., studies of the affected members of the K.E. family have shown that when they perform a verb generation task they have diffuse bilateral brain activation), in contrast to unaffected individuals, who show more focal activation of traditional language regions in the left hemisphere (Vargha-Khadem, Gadian, Copp, & Mishkin, 2005). Electrophysiological methods have been used to study brain– behavior relationships in children with SLI, but results are characterized by the same level of inconsistency as is seen in the structural imaging studies (see chapter 17; Bishop & McArthur, 2005; Bishop, 2007). Furthermore, research in this field is handicapped by a lack of normative data on typically developing children. Cognitive Factors Theoretical accounts of SLI have traditionally attempted to explain the disproportionate difficulties with grammar that characterize the disorder. Many of these theories are grounded in a linguistic tradition and propose that SLI results from a delay or disruption of the development of a specialized brain system that serves grammatical computations (Rice, 2004; van der Lely, 2005). Tasks tapping grammatical marking of tense and agreement, as well as comprehension of complex grammatical relations, discriminate children with SLI and typically developing peers (Conti-Ramsden, 2003) and poor performance on grammatical tasks has been put forward as a behavioral marker of heritable forms of SLI (Rice, 2004). However, a number of researchers have criticized the notion of an innate modular language faculty and suggest that specialized language function is the developmental outcome of a number of domain-general endowments acting in concert (Bates, 2004). Children with SLI are impaired not only on SPEECH AND LANGUAGE DISORDERS 795 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 795

grammatical tasks, but also on measures of phonological shortterm memory. These tasks require children to repeat strings of unfamiliar speech sounds (e.g., “blonterstaping”), an ability that is seen to facilitate the learning of new words (Baddeley, Gathercole, & Papagno, 1998). Attention has also been focused on the abilities of children with SLI to process rapid brief auditory signals (Tallal, 2000); an ability that is argued to underpin the recognition and learning of grammatical contrasts in English (Joanisse & Seidenberg, 2003). A recent study confirmed that deficits in nonsense word repetition, like deficits in grammatical inflection, are highly heritable and sensitive markers of SLI (Bishop, Adams, & Norbury, 2006a). Intriguingly, there appeared to be little etiological overlap between the two deficits, indicating that different risk genes may be involved in these different aspects of language difficulty. However, auditory processing deficits showed no genetic influence (Bishop, Bishop, Bright et al., 1999) and cannot fully account for the linguistic deficits seen in SLI (Norbury, Bishop, & Briscoe, 2001; van der Lely, Rosen & Adlard, 2004). Thus, auditory impairment may be seen as an environmentally based risk factor that comes into play in those children at genetic risk of the disorder. The conclusions that we draw from theoretical studies of SLI are that there is unlikely to be a single cognitive or biological factor that can cause the variety of language profiles captured by a diagnosis of SLI. Instead, multiple risk factors in the child’s genetic and biological make-up are likely to interact with factors in the child’s environment to determine the severity and course of language impairment (Bishop, 2006). Intervention and Prognosis for Specific Language Impairment Intervention is usually determined by speech and language therapists, who use a wide range of techniques to stimulate language learning. In preschool, intervention may involve working with parents and caregivers to provide optimal language input for the child. Such approaches often involve videotaping parent–child interactions and using these videos constructively to foster better communication techniques (e.g., The Hanen program; Girolametto & Weitzman, 2006; see www.hanen.org for details). The advice given focuses on following the child’s lead in play, talking about what the child is doing rather than asking questions, recasting what the child says in a grammatically correct form, and increasing communication opportunities by giving children choices rather than anticipating their needs. In a meta-analysis of intervention, Law, Garrett, & Nye (2004) found that treatment for preschool children with expressive language delays was successful when compared with no treatment, and treatments lasting longer than 8 weeks produced the most favorable outcomes. Parent-led interventions were as successful as direct intervention by a speechlanguage therapist in developing young children’s language; such interventions are cost-effective and encourage generalization of language gains into everyday environments. With such methods, speech-language therapists are instrumental in identifying communicative targets for parents to work on, and supporting parents throughout the intervention program. Nevertheless, as noted by Nelson, Nygren, Walker, and Panoscha (2006), there is a dearth of good-quality research on long-term efficacy of interventions for preschool children, a problem that is compounded by the fact that existing studies are small and heterogeneous. There is even less research on intervention for children with receptive language difficulties or school-aged children. In general, randomized controlled studies are rare and studies that explicitly compare different treatment approaches for the same language problem simply do not exist. The field is plagued by studies in which the participant numbers are small, the interventions poorly described and methodological problems abound. The studies outlined below are pilot studies in nature, but offer promise for larger-scale investigations of treatment efficacy. Ebbels (2007) reported preliminary data for a school-based intervention that focuses on grammar. This intervention uses visual cues such as shapes and colors to teach children with language impairment different parts of speech, and how these parts of speech may combine in different grammatical constructions. By situating the intervention in a school setting, classroom materials can be used in therapy to promote generalization. Other approaches advocate developing the child’s linguistic repertoire in more naturalistic settings. Fey, Long, and Finestack (2003) presented 10 principles for facilitating grammar development. Although the authors recognize the need to teach specific grammatical forms, they argue that these forms should rarely be taught in isolation. Instead, the targeted forms should be embedded in natural contexts such as play or story-telling. The role of the therapist in this approach is to manipulate the environment so that the targeted form is salient and frequently occurring, providing ample opportunity for modeling and shaping the child’s production. Adams (2005) reported a series of case studies detailing treatment for children with pragmatic language impairments. Standardized assessments often lack the sensitivity to detect subtle improvements in social communication and interaction, but using detailed conversational analysis, Adams was able to demonstrate improvement in discourse functioning in schoolaged children. These studies lacked a suitable control group necessary to evaluate specific treatment effects, but hold promise for larger-scale studies with school-aged populations with pragmatic deficits. A radically different approach to treatment was developed by Tallal, Miller, Bedi et al. (1996), who devised a computerbased intervention, FastForWord, which involves prolonged and intensive training on specific components of language and auditory processing. The advantage of computerized presentation is that children may be persuaded to participate in thousands of training trials in a way that would not be possible in standard therapist-based interventions. Unfortunately, after initially promising results using the FastForWord program (Merzenich, Jenkins, Johnston et al., 1996), randomized controlled studies have failed to demonstrate a significant CHAPTER 47 796 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 796

advantage of this approach over other methods in improving children’s language or literacy skills (Cohen, Hodson, O’Hare et al., 2005; Pokorni, Worthington, & Jamison, 2004; Rouse & Krueger, 2004). Children in these studies had receptive as well as expressive language impairments, which appear particularly resistant to treatment (Law, Garrett, & Nye, 2004). The limited intervention studies available suggest that there is no cure for SLI. Despite years of intensive specialist training, many children will continue to have language deficits. However, one should bear in mind the broader aims of therapeutic intervention for SLI. One cannot “cure” a sensorineural hearing loss or a physical impairment; in these instances intervention will seek to maximize potential and lessen the impact of the child’s impairment on his or her social well-being and educational experiences. In the absence of a “quick-fix,” many children with SLI will present with long-term special educational needs. There is a lack of consensus on the most suitable type of provision for children with SLI. Experience in the UK suggests that some children will benefit from a special school or language unit placement where there is access to regular speech and language therapy and where the curriculum may be supported by using signed English or a visual symbol system. Others will benefit from a mainstream placement. Unfortunately, specialist support for children within mainstream settings is limited and almost non-existent by secondary school (Lindsay, Dockrell, Mackie, & Letchford, 2005). A number of longitudinal studies have shed light on the developmental course of SLI. There is general agreement that the child with severely impaired understanding of language has a poor prognosis, even if the diagnosis is made early. Comprehension problems do not resolve spontaneously and, as they grow older, children with such problems experience increasing difficulties with social cognition and interaction (Clegg, Hollis, Mawhood, & Rutter, 2005; Howlin, Mawhood, & Rutter, 2000), non-verbal reasoning (Botting, 2005; Stothard, Snowling, Bishop et al., 1998) and an increased risk of psychiatric disturbance (Howlin, Mawhood, & Rutter, 2000; Snowling, Bishop, Chipchase, & Kaplan, 2006). For children with normal non-verbal abilities and expressive language impairments, the outlook is much more positive, particularly if expressive deficits have resolved by school entry (Stothard, Snowling, Bishop et al., 1998). However, there is evidence that literacy skills may remain an area of weakness for these children (Botting, Simkin, & Conti-Ramsden, 2006; Rescorla, 2005); although these “resolved” cases may score within the normal range on standardized assessment, their scores are frequently lower than those of an IQ-matched peer group. Conclusions This chapter has considered various factors designed to facilitate clinical decision-making in this complex and difficult area. It is important to realize that cases of “pure” SLI are rare in clinical practice. Rather, children present with a range of cooccurring deficits and challenges that may cloud diagnostic decisions. The most important message for clinicians to remember is that speech, language and communication skills are critical to the cognitive and social development of children, whatever their primary diagnosis. Thus, attention to these aspects of development is fundamental for children presenting to psychiatric clinics. Further Reading Beitchman, J. H., Cohen, N. J., Konstantareas, M. M., & Tannock, R. (Eds.). (1996). Language, learning, and behavior disorders. Cambridge: Cambridge University Press. Bishop, D. V. M. (1997). Uncommon understanding: Development and disorders of language comprehension in children. Hove: Psychology Press. McCauley, R. J., & Fey, M. E. (Eds.). (2006). Treatment of language disorders in children. Baltimore: Paul H. Brookes. [Includes examples on DVD.] Paul, R. (2006). Language disorders from infancy through adolescence: Assessment and intervention (3rd edn.). St. Louis: Mosby-Year Book. References Adams, C. (2005). Pragmatic language impairment: case studies of social and pragmatic language therapy. Child Language Teaching and Therapy, 21, 227–250. Adams, C., Cooke, R., Crutchley, A., Hesketh, A., & Reeves, D. (2001). Assessment of comprehension and expression (6–11). Windsor: NFER-Nelson. Adams, C., Green, J., Gilchrist, A., & Cox, A. (2002). Conversational behaviour of children with Asperger syndrome and conduct disorder. Journal of Child Psychology and Psychiatry, 43, 679–690. American Psychiatric Association. (2000). Diagnostic and statistical manual of mental disorders (4th edn.). Text revision. Washington, DC: American Psychiatric Association. Baddeley, A., Gathercole, S., & Papagno, C. (1998). The phonological loop as a language learning device. Psychological Review, 105, 158–173. Baird, G., Simonoff, E., Pickles, A., Chandler, S., Loucas, T., Meldrum, D., et al. (2006). Prevalence of disorders of the autism spectrum in a population cohort of children in South Thames: The Special Needs and Autism Project (SNAP). Lancet, 368, 210–215. Bates, E. A. (2004). Commentary: Explaining and interpreting deficits in language development across clinical groups: Where do we go from here? Brain and Language, 88, 248–253. Beitchman, J. H., Brownlie, E. B., & Wilson, B. (1996). Linguistic impairment and psychiatric disorder: Pathways to outcome. In J. Beitchman, N. J. Cohen, M. M. Konstantareas, & R. Tannock (Eds.), Language, learning and behavior disorders: Developmental, biological and clinical perspectives (pp. 493–514). New York: Cambridge University Press. Bird, J., Bishop, D. V. M., & Freeman, N. (1995). Phonological awareness and literacy development in children with expressive phonological impairments. Journal of Speech and Hearing Research, 38, 446–462. Bishop, D. V. M. (1994). Is specific language impairment a valid diagnostic category? Genetic and psycholinguistic evidence. Philosophical Transactions of the Royal Society, Series B, 346, 105–111. Bishop, D. V. M. (2000). Pragmatic language impairment: A correlate of SLI, a distinct subgroup, or part of the autistic continuum? In D. V. M. Bishop, & L. B. Leonard (Eds.), Speech and language impairments in children: Causes, characteristics, intervention and outcome (pp. 99–114). Hove: Psychology Press. Bishop, D. V. M. (2001). Genetic and environmental risks for specific language impairment in children. Philosophical Transactions of the Royal Society, Series B, 356, 369–380. SPEECH AND LANGUAGE DISORDERS 797 9781405145497_4_047.qxd 29/03/2008 02:54 PM Page 797

Bishop, D. V. M. (2002). Motor immaturity and specific speech and language impairment: Evidence for a common genetic basis. American Journal of Medical Genetics: Neuropsychiatric Genetics, 114, 56–63. Bishop, D. V. M. (2003a). The Children’s Communication Checklist – 2. London: Harcourt Assessment. Bishop, D. V. M. (2003b). The Test for Reception of Grammar, version 2 (TROG-2). London: Harcourt Assessment. Bishop, D. V. M. (2004). Expression, Reception and Recall of Narrative Instrument (ERRNI). London: Harcourt Assessment. Bishop, D. V. M. (2005). DeFries–Fulker analysis of twin data with skewed distributions: Cautions and recommendations from a study of children’s use of verb inflections. Behavior Genetics, 35, 479– 490. Bishop, D. V. M. (2006). Developmental cognitive genetics: How psychology can inform genetics and vice versa. Quarterly Journal of Experimental Psychology, 59, 1153–1168. Bishop, D. V. M. (2007). Using mismatch negativity to study central auditory processing in developmental language and literacy impairments: Where are we, and where should we be going? Psychological Bulletin, 133, 651–672. Bishop, D. V. M., Adams, C. V., & Norbury, C. F. (2006a). Distinct genetic influences on grammar and phonological short-term memory deficits: Evidence from 6-year-old twins. Genes, Brain and Behavior, 5, 158–169. Bishop, D. V. M., Bishop, S. J., Bright, P., James, C., Delaney, T., & Tallal, P. (1999). Different origin of auditory and phonological processing problems in children with language impairment: Evidence from a twin study. Journal of Speech, Language and Hearing Research, 42, 155–168. Bishop, D. V. M., Laws, G., Adams, C., & Norbury, C. F. (2006b). High heritability of speech and language impairments in 6-year-old twins demonstrated using parent and teacher report. Behavior Genetics, 36, 173–184. Bishop, D. V. M., & McArthur, G. M. (2005). Individual differences in auditory processing in specific language impairment: A followup study using event-related potentials and behavioural thresholds. Cortex, 41, 327–341. Bishop, D. V. M., Maybery, M., Wong, D., Maley, A., Hill, W., & Hallmayer, J. (2004). Are phonological processing deficits part of the broad autism phenotype? American Journal of Medical Genetics. Part B, Neuropsychiatric Genetics, 128, 54–60. Bishop, D. V. M., & Norbury, C. F. (2002). Exploring the borderlands of autistic disorder and specific language impairment: A study using standardised diagnostic instruments. Journal of Child Psychology and Psychiatry, 43, 917–929. Bishop, D. V. M., North, T., & Donlan, C. (1995). Genetic basis of specific language impairment: Evidence from a twin study. Developmental Medicine and Child Neurology, 37, 56–71. Bishop, D. V. M., & Snowling, M. J. (2004). Developmental dyslexia and specific language impairment: Same or different? Psychological Bulletin, 130, 858–886. 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802 Learning difficulties can occur in the context of global delays in development or where there are circumscribed deficits in specific cognitive processes. It has proven productive in theory and in practice to differentiate these two forms of learning difficulties (Rutter & Maughan, 2005). The term specific learning difficulties is used to refer to poor educational attainment in the absence of general cognitive deficits, whereas the term general learning difficulties (now more appropriately termed intellectual disability; see chapter 49) is used to refer to problems associated with low IQ. This chapter deals with specific learning difficulties, the major focus being on reading difficulties. More research has been conducted on the nature and causes of reading difficulties than on other learning difficulties, and interventions to ameliorate reading impairments have been evaluated. The chapter also considers specific difficulties in arithmetic and non-verbal learning disabilities including motor impairments; much less is known about the causes and treatments of these other learning disorders. The assessment of specific learning difficulties is more often the domain of psychologists and educators than of psychiatrists and hence, the term “difficulties” is usually used rather than “disorders” or “disabilities,” which derive from the medical model. According to diagnostic manuals, there is a variety of such difficulties, viz, reading disorder, spelling disorder, mathematical disorder, disorder of written expression and mixed disorder of scholastic skills (DSM-IV, American Psychiatric Association, 2000). However, there is not a oneto-one correspondence between the classifications specified in the diagnostic manuals and those typically used by school systems or researchers in the field. Importantly, “discrepancy definitions” (that prescribe that attainments should be low relative to age and intelligence) are seldom strictly adhered to; in particular, the measurement of IQ is no longer considered central to the diagnosis of reading disorders. The main reason for this is that there are few cognitive differences relevant to reading between poor readers of high and low IQ. Given targeted support, children with specific reading difficulties make similar progress in reading (as measured by decoding) to those with general reading difficulties (Hatcher & Hulme, 1999; Shaywitz, Fletcher, Holahan, & Shaywitz, 1992a). However, in the absence of such intervention, outcomes for reading and spelling have been reported to differ, children with intellectual disability faring better in literacy although less well in arithmetic (Rutter & Maughan, 2005). Disorders of Reading and Spelling Definition, Classification and Incidence Difficulties in reading accuracy (measured by tasks requiring decoding of single words) are distinct from difficulties with reading comprehension (measured by tasks tapping understanding of text). Whereas problems with decoding inevitably limit reading comprehension, there are a substantial minority of children (perhaps as many as 10%; Nation, 2005) who have difficulties with reading comprehension in the absence of problems with reading accuracy. In English-speaking countries, reading difficulties have been reported to affect 4–8% of schoolaged children. Epidemiological studies in England reported prevalence rates of just over 3% (3.1% on tests of reading accuracy and 3.6% on tests of reading comprehension) among 9- and 10-year-olds in a non-metropolitan area using a stringent IQ-discrepancy criterion of 2 standard errors of prediction below expected performance (Rutter & Yule, 1975). Using exactly comparable assessment procedures, rates were more than doubled (6.3% for reading accuracy and 9.3% for reading comprehension) in an inner city area, suggesting that social factors have a key role in risk for reading disability (Rutter & Maughan, 2005; Yule, Rutter, Berger, & Thompson, 1974). Boys are more likely to be referred for reading difficulties than girls (Shaywitz, Shaywitz, Fletcher, & Escobar, 1990) but this is not simply a matter of referral bias because sex ratios of between 1.5:1 and 3:1 boys to girls have been reported in large-scale community studies (Rutter, Caspi, Fergusson et al., 2004). However, rates of reading difficulties vary with age (Shaywitz, Escobar, Shaywitz, Fletcher, & Makugh, 1992b) with some children falling just below a chosen threshold at one age and just above at another. Problems with word decoding are likely to predominate in the earliest years of schooling, whereas a later-emerging group of poor readers who cope with the initial stages of learning to read fare less well when the school curriculum places heavier emphasis on comprehension. Later still, through into adulthood, individuals may face persisting problems with spelling or written expression (Maughan, Messer, Collishaw et al., submitted). Reading and Other Specific Learning Difficulties Margaret J. Snowling and Charles Hulme 48 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 802 Rutter’s Child and Adolescent Psychiatry, 5th Edition, Edited by M. Rutter, D. V. M. Bishop D. S. Pine, S. Scott, J. Stevenson, E. Taylor and A. Thapar © 2008 Blackwell Publishing Limited. ISBN: 978-1-405-14549-7

READING AND OTHER SPECIFIC LEARNING DIFFICULTIES 803 The language in which children learn to read also affects the likelihood of reading difficulties, although data do not exist to allow fair comparison of prevalence rates. European languages vary in the consistency of their writing systems. Languages such as Italian, German and Greek are regular in the way they map speech sounds onto written forms, whereas others – most notably English (and to a lesser extent Danish and French) are more irregular or opaque. Regular orthographies present children with fewer challenges in learning to read than do opaque writing systems (Seymour, 2005). However, differences in diagnostic practice may have overemphasized the differences between reading difficulties in different languages and played down the similarities (Caravolas, 2005). In both the irregular English and the regular Czech language, the correlates of reading skill and the predictors of reading difficulties have been reported to be similar (Caravolas, Volin, & Hulme, 2005). In line with this, a recent survey of 150,000 Dutch children reported a 9% prevalence of reading and spelling problems among 11- to 12-year-olds, and further assessment revealed that these were specific to literacy (and not more general) for 3.6% of children (Blomert, 2005). The case might be thought different when considering reading difficulties in non-alphabetic languages, such as Chinese, but there is little direct evidence that supports this view (Hanley, 2005). Normal Literacy Development: A Framework In an alphabetic language such as English, the foundation of literacy is a system of mappings between orthography (the letters of printed words) and phonology (the speech sounds of spoken words). Learning to read requires the child to abstract the idea that the letters of printed words represent phonemes in spoken words (Byrne, 1998). More formally, the relationship between oral and written language skills has been simulated in computational models. According to the Triangle model of Plaut, McClelland, Seidenberg et al. (1996; after Seidenberg & McClelland, 1989) depicted in Fig. 48.1, reading involves the interaction of a phonological pathway (mapping from letters to sounds) and a semantic pathway (mapping from letters to meanings and then to sounds). It is thought that beginning readers place most reliance on the phonological pathway (phonics) and then gradually start to use the semantic pathway to gain fluency in their reading. This use of the semantic pathway is important in English for reading exception words that do not conform to English letter-sound rules (e.g. yacht and pint). When children read words they usually occur in a sentence context; context exerts its influence on reading via activation through the semantic pathway. The Triangle model makes predictions about the cognitive resources that children require in order to learn to read. It is now agreed that early reading development depends on phoneme awareness (the ability to reflect on and manipulate speech sounds in words) and letter knowledge (Bowey, 2005). Later in development, broader language skills (such as vocabulary and grammar) predict gains in reading fluency and are critical foundations for reading comprehension (Catts, Fey, Zhang, & Tomblin, 1999; Muter, Hulme, Snowling, & Stevenson, 2004; Share, 1995). In addition, higher-level skills, such as inference making, are important for some aspects of text comprehension (Yuill & Oakhill, 1991). Thus, reading difficulties can occur for different reasons. Problems of Decoding Problems that specifically affect a child’s ability to decode text are commonly referred to as “dyslexia.” Although the term has had a chequered history, international voluntary agencies concerned with children’s specific reading difficulties now provide definitions of the “disorder” that are informed by research (International Dyslexia Association, 2002) and national initiatives (Riddick, 2006) have lent credence to the judicious use of the term. Theories of Dyslexia Phonological Deficit Theory The majority of children with specific reading difficulties have phonological (speech processing) difficulties that affect their decoding skill to some extent (Vellutino, Fletcher, Snowling, & Scanlon, 2004). The predominant theoretical account views the primary cognitive cause of dyslexia as a phonological (speech) processing impairment (Harm & Seidenberg 1999; Ramus, Rosen, Dakin et al., 2003). According to this hypothesis, children with dyslexia have difficulty establishing the phonological reading pathway (Snowling, 2000); the development of the semantic pathway is affected less because the mappings in this pathway do not depend upon identifying the phonemes of speech. Aside from reading, phonological deficits explain why people with dyslexia typically have difficulties with a wide range of cognitive tasks that engage phonological processes such as limitations of verbal short-term memory, long-term verbal (phonological) learning, slow naming of letters, digits, color and Fig. 48.1 The Triangle framework. [After Seidenberg & McClelland, 1989.] Context Semantics (meaning) Orthography (print) Phonology (speech) 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 803

CHAPTER 48 804 objects and word finding difficulties. Together, this evidence led Stanovich and colleagues to propose the phonological-core variable-difference model of dyslexia (Stanovich & Siegel, 1994); according to this model poor phonology is related to poor reading performance, irrespective of IQ. It is now believed that this model holds irrespective of language background (Caravolas, 2005; Goulandris, 2003). Rate Deficits and Double Deficits Some have argued that the phonological deficit theory does not fully account for the reading problems found in children with dyslexia. Lovett, Ransby, and Barron (1988) differentiated accuracy-impaired and rate-impaired poor readers, and Wolf and Bowers (1999) distinguished between disabled readers with single deficits in either phonological awareness or in naming speed (measured by the speed to retrieve names of digits or letters; Wimmer, Mayringer, & Landerl, 2000) and a subgroup with deficits in both processes. An alternative to the phonological deficit hypothesis is the automatization hypothesis (Nicolson & Fawcett, 1990). According to this theory, people with dyslexia have difficulty learning skills to the point at which they become completely automatic, and, although they can learn to read, they have difficulty developing reading fluency. This model conceptualizes the phonological deficit in dyslexia as a consequence of problems with speech-articulation. A feature that marks this hypothesis out from the phonological deficit hypothesis is that it places the deficit in dyslexia at a domain-general level – that is, the automatization deficit places similar constraints on the learning of all skills, including basic motor skills, and is associated with cerebellar dysfunction (Nicolson, Fawcett, & Dean, 2001). The theory does not account well for the finding that dyslexia can occur in the absence of motor deficits. Perceptual Theories of Dyslexia A large body of research has assessed whether reading difficulties are associated with low-level perceptual processing impairments. Investigations have examined putative impairments in visual, auditory and motor domains as explanations for different manifestations of dyslexia. Visual Deficits Although most people with reading difficulties have normal visual acuity, there is a raised incidence of abnormalities on psychophysical tasks assessing motion processing and contrast sensitivity (Skoyles & Skottun, 2004). These impairments have been related to a deficit within the magnocellular division of the visual system, which responds to rapid changes in visual stimulation and to moving stimuli (Lovegrove, Martin, & Slaghuis, 1986; Stein & Talcott, 1999). However, some studies have found no evidence of abnormal sensitivity, whereas others have suggested that group differences may be related to uncontrolled differences in IQ (Hulslander, Talcott, Witton et al., 2004). Problems of visual attention have also been considered a putative cause of dyslexia (Facoetti, Turatto, Lorusso, & Mascetti, 2001; Hari, Renvall, & Tanskanen, 2001; Roach & Hogben, 2004) but again the evidence is inconsistent. It has therefore been proposed that phonological and visual attention could be dissociable causes of dyslexia that may co-occur (Valdois, Bosse, & Tainturier, 2004). Although scientific understanding of how visual deficits might affect reading is limited, the use of colored lenses or filters to reduce visual stress and improve reading performance is recommended by some practitioners. To date, there is no evidence for the effectiveness of such interventions as a treatment for reading impairments in dyslexia. Auditory Deficits A hypothesis that has attracted considerable research is that the phonological deficit in dyslexia stems from a deficit in basic auditory processing (Tallal, 1980); specifically, an auditory processing deficit affects the perception of consonants, which in turn affects the development of phonological skills (cf. Mody, 2003). The plausibility of this hypothesis is supported by evidence that infants at family risk of dyslexia or language impairment are less sensitive to the speech sounds that signal meaning changes than typically developing children (Leppänen, Eklund, & Lyytinen, 1997), and that behavioral and brain responses to speech sounds in the first year of life correlate with later language and reading development (Guttorm, Leppänen, Poikkeus et al., 2005). Investigation of auditory deficits has extended to tasks tapping frequency discrimination, frequency modulation, binaural processing, backward masking (for review see Bailey & Snowling, 2002) and amplitude onset sensitivity (Goswami, Thomson, Richardson et al., 2002). However, the findings are inconsistent and typically only 30–40% of people with dyslexia show auditory impairments. The direct investigation of speech perception in dyslexia has produced some positive findings (Manis, McBride-Chang, Seidenberg et al., 1997). Current evidence comes primarily from performance on categorical perception tasks (e.g., identifying synthetic speech tokens as [ka] or [ga]). As a group, children with dyslexia show fuzzy boundaries between different phonemes, constituting a categorical speech perception deficit (it should be noted that such difficulties are more marked if children have concomitant language impairments; see chapter 47; Joanisse, Mains, Keating, & Seidenberg, 2000). Serniclaes, Van Heghe, Mousty, Carré, & SprengerCharolles (2004) showed that not only did children with dyslexia show reduced between-category discrimination, but also they were more sensitive to (within category) variations in the acoustic characteristics of individual phonemes than age-matched controls. Such hypersensitivity implies that phoneme categories are not well-defined and this in turn may pose important problems for learning to read in all alphabetic systems that depend on knowledge of how phonemes are related to letters. Overall, evidence for the involvement of perceptual problems in dyslexia is equivocal; findings suggest that neither auditory nor visual (nor cerebellar) deficits are necessary or sufficient causes of dyslexia (Ramus, Rosen, Dakin et al., 2003; White, Milne, Rosen et al., 2006). However, in the absence of longitudinal data it remains possible that a sensory deficit early 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 804

in development (which may resolve by the time children are diagnosed as having reading problems) may still have had a causal role in the etiology of the disorder. Spelling Difficulties Typically, the spelling difficulties of people with dyslexia are more severe and more resistant to remediation than their reading difficulties (Romani, Olson, & DiBetta, 2005). Such problems may be seen as a direct consequence of difficulties in mastering the mappings between orthography (spelling patterns) and sound within the phonological pathway (Fig. 48.1). The spelling errors made by people with dyslexia include both phonetic spelling errors, where the sound pattern of the word is represented accurately (e.g., biscuit → biskit; chaos → kaos), and phonetically unacceptable spelling errors (e.g., umbrella → unbrl; adventure → afveorl). The term dyslexia has sometimes been applied to individuals who have spelling difficulties in the absence of reading problems. These children (called “dysgraphic”; Frith, 1980) tend to have higher verbal than performance IQ and they make phonetically accurate spelling errors (Nelson & Warrington, 1974; Romani, Olson, & Di Betta, 2005). Evidence from single-case studies suggests they may have subtle visual memory impairments (Goulandris & Snowling, 1991; Romani, Ward, & Olson, 1999). This cognitive profile has also been observed in “unaffected” offspring of parents with dyslexia, suggesting that it may represent a broader phenotype of dyslexia in which good oral language skills have mitigated the risk of reading problems (Snowling, Muter, & Carroll, 2007). Reading Comprehension Impairments In contrast to children with dyslexia, “poor comprehenders” decode well but have problems understanding what they read. Their difficulties often go unnoticed in the classroom because they can read aloud competently. Poor comprehenders typically have normal non-verbal abilities and good phonology; they do well on phoneme awareness tasks and on simple memory tests (Nation, 2005). However, they have cognitive impairments that encompass poor working memory, problems making inferences and deficits in metacognitive processes, such as comprehension monitoring (Cain, Oakhill, Barnes, & Bryant, 2001; Cain, Oakhill, & Bryant, 2004). Clinically, the profile is often seen in combination with attention deficit/hyperactivity disorder (ADHD). Within the Triangle model, poor comprehenders have problems both within the semantic pathway and in grammatical processes that feed it. The consequences are a tendency to rely heavily on a “phonic” approach, leading to the tendency to regularize words (e.g., to read broad as “brode” or bread as “breed”), a reduction in the benefit of context (i.e., limited semantic facilitation of word reading) and problems of reading comprehension – their defining characteristic. The reading comprehension impairments shown by these children are related to a range of oral language processing weaknesses (see chapter 47; Nation, Clarke, Marshall, & Durand, 2004). Etiology of Reading Difficulties Genetic Influences on Dyslexia Prospective studies following the development of children born to parents with dyslexia confirm a heightened risk of literacy impairment in “dyslexic” families (Lyytinen, Erskine, Tolvanen et al., 2006; Scarborough, 1990; Snowling, Gallagher, & Frith, 2003). However, families share environments as well as genes, and twin studies can be helpful in disentangling genetic and environmental influences on reading behavior (see chapter 23). Twin studies of dyslexia find that the proportion of variance attributable to genetic factors (heritability) is significant (Pennington & Olson, 2005), and heritability appears to be higher among more severely disabled readers (Bishop, 2001) and among those with higher IQ (Olson, Datta, & DeFries, 1999). Two relatively small-scale British twin studies have reported that shared environment accounted for most of the variance in reading, once IQ had been controlled for (Bishop, 2001; Stevenson, Graham, Fredman, & McLoughlin, 1987), perhaps reflecting more diverse educational experiences in these samples. Moreover, it is important to bear in mind that some of the shared genetic variance between twins may be caused by gene–environment correlation (Rutter, 2006). For example, the home literacy background provided by more literate parents may foster reading skills, and better readers may themselves actively seek out more literary experiences. Studies of the molecular basis of genetic influences on reading have used a variety of methods (for reviews see Fisher & DeFries, 2002; Grigorenko, 2005). To date, the strongest evidence for linkage with dyslexia (in terms of number of replications) is a site on the short arm of chromosome 6. Other linkages that have been replicated although less frequently are on chromosomes 1, 2, 3, 11, 15 and 18 (Grigorenko, 2005). Recently, some candidate susceptibility genes have been identified within these chromosomal regions, including K1AA0319 on 6p (Cope, Harold, Hill et al., 2005) and DYX1C1 in the 15q21 region (Taipale, Kaminen, Nopola-Hemmi et al., 2003). However, it is important to remember that genetic influences are probabilistic; complex disorders depend on the combined influence of many genes of small effect, as well as on environmental influences. Moreover, the findings of linkage studies depend upon the behavioral phenotype, such that the use of different definitions of dyslexia by different groups will affect the genotypes that are identified (particularly when data are taken from children learning to read in different languages). To date, there is no comparable analysis of the genetic bases of reading comprehension difficulties. However, work on the genetic basis of specific language impairments is likely to be relevant here (SLI Consortium, 2002, 2004). Brain Bases of Dyslexia The majority of children with specific reading difficulties do not show any gross structural brain abnormalities, but early neurodevelopmental abnormalities appear to be involved (Galaburda, 1994; Galaburda & Kemper, 1978). It has been reported that there are a wide range of structural brain READING AND OTHER SPECIFIC LEARNING DIFFICULTIES 805 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 805

differences between people with dyslexia and controls (Eckert, 2004) and an “anatomical risk index” comprising measurements taken from the brain regions implicated in dyslexia has been reported to distinguish between people with specific decoding difficulties and those with poor reading comprehension (Leonard, Eckert, Lombardino et al., 2001, Leonard, Eckert, Given et al., 2006). Functional brain imaging studies have contributed to understanding of the brain bases of dyslexia (see chapter 11). Findings indicate that children and adults with dyslexia typically show less activity than controls in left hemisphere temporo-parietal cortex when reading (Price & McCrory, 2005; Shaywitz, Shaywitz, Blachman et al., 2004), and preliminary evidence suggests that intervention may reduce this underactivation (Simos, Fletcher, Bergman et al., 2002). The causal status of brain differences in dyslexia is debatable because brain development shows considerable plasticity and both its structure and function are shaped by use (Johnson, 2005). A reasonable conclusion is that the brain differences between dyslexic and normal readers reflect the interplay of genetic influences and environmental experiences on brain development. Social and Environmental Influences on Reading Development and Disorder Home and School Background It is important not to overlook the critical role of the environment in shaping a child’s reading development (Phillips & Lonigan, 2005). Evidence indicates that reading disorders show a strong social gradient that is not entirely attributable to differences in phonological skills or general intellectual abilities (Hecht, Burgess, Togesen, Wagner, & Rashotte, 2000), and poor readers often come from large families, where later-born children may face delays in language development (see chapter 47). One aspect of delayed language development is poor vocabulary, a mediator of deficits in phoneme awareness (Carroll, Snowling, Hulme, & Stevenson, 2003). Direct literacy-related activities in the home are also important (Whitehurst & Lonigan, 1998), although these primarily affect reading comprehension, via vocabulary growth (Stevenson & Fredman, 1990). Traditional definitions of dyslexia excluded children whose reading failure was caused by “inadequate opportunity to learn,” but how to interpret this is unclear. Comparisons of children from the same catchment area attending different schools have emphasized that schooling can make a substantial difference to reading achievement (Rutter & Maughan, 2002). Equally, school experience can differ markedly between good and poor readers. Cross-linguistic Manifestations of Reading Disorders Aside from the home and school environment, an important macro-environmental influence on reading development is the language in which a child learns (Harris & Hatano, 2000). The reading and spelling symptoms of dyslexia vary across orthographies; in languages such as German or Italian, reading difficulties are identified by slow rates of reading (few reading errors occur), whereas in English poor reading accuracy is the primary behavioral marker (Landerl, Wimmer, & Frith, 1997). However, reading universally is a process involving the mapping of visual characters on to phonological forms; it follows that children with phonological impairments are at risk of reading difficulties in all languages. Gene–Environment Correlation and Reading Practice Aside from the above, being a poor reader affects the motivation to read. From very early in development, children differ in their interest in books, and children at risk of dyslexia may well be among those who are more difficult to engage. Where parents themselves have literacy problems, this might also set the stage for less than optimal reading-related experiences in the home (cf. Petrill, Deater-Deckard, Schatsneider, & Davis, 2005). One variable that can have a significant impact on the behavioral manifestation of a reading disorder is reading practice. Measures of “print exposure” (assessed by questionnaires that require participants to differentiate real book titles or real authors’ names from distracter items, and which document reading habits) account for variance in reading skills when other critical variables such as IQ and phonological awareness have been controlled (Cunningham & Stanovich, 1990). Print exposure measures are simply a proxy for the amount of reading done and it is likely that the effects of low exposure are cumulative, causing reader-differences in reading competence to become magnified over time. In summary, as might be expected for a complex trait such as reading, the etiology of reading disorders is varied and depends on both genetic and environmental factors. It is critical to distinguish between problems with decoding and problems of reading comprehension. Some children carry a genetic risk of dyslexia but whether or not they are classified as dyslexic depends upon the particular language and school context in which they learn and the other skills (or deficits) they bring to the task of reading. In keeping with this, there is currently a move away from single-deficit toward multifactorial models that explain the nature and causes of dyslexia (Pennington, 2006). Language-Learning Impairments In recent years, there has been a growing tendency to collapse together disorders of reading (primarily dyslexia) with disorders of speech and language development, reflecting the clinical impression of considerable behavioral overlap between these disorders and their effects on academic performance. However, this is a retrograde step. Children with speech and language impairments are at high risk of reading problems be they children at family risk of dyslexia (Lyytinen, Erskine, Tolvanen et al., 2006; Pennington & Lefly, 2001; Scarborough, 1990; Snowling, Gallagher, & Frith, 2003), children with specific language impairment (Bishop & Adams, 1990; Catts, Adlof, Hogan, & Weismer, 2005; Snowling, Bishop, & Stothard, 2000) or children with speech sound disorders (see chapter 47; Bird, Bishop, & Freeman, 1995; Nathan, CHAPTER 48 806 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 806

READING AND OTHER SPECIFIC LEARNING DIFFICULTIES 807 Stackhouse, Goulandris, & Snowling, 2004; Raitano, Pennington, Tunick, & Broada, 2004). The nature of the risk depends on a number of factors including the pervasiveness and persistence of the speech-language impairment. In order to understand the relationship between the different disorders, Bishop and Snowling (2004) proposed a two-dimensional model (Fig. 48.2). Within this model, the risk of word-level decoding deficits is related to phonological skills (that vary from good to poor) and the risk of reading comprehension deficits is related to language skills beyond phonology (grammar and vocabulary, again varying from good to poor). This two-dimensional model has direct implications for the assessment and management of children’s reading difficulties and suggests that concerns over whether a particular child fulfills the diagnostic criteria for a specific reading disorder may be of little importance – there are continuous variations in reading skills in the general population and children with either decoding or reading comprehension problems will benefit from appropriate educational interventions which need to be tailored to individual children’s needs. Problems of Numeracy Definition, Classification and Incidence Children experience different kinds of difficulty with numeracy skills. Some affect arithmetic (computation) whereas others affect more conceptual aspects of mathematics that require problem-solving. However, these are not well differentiated either in diagnostic manuals or in practice; tests of number skills differ in the extent to which they assess basic arithmetic as opposed to mathematical concepts (e.g., numerosity, magnitude, commutativity or geometry) and this leads to an unhelpful tendency to categorize all mathematical difficulties together. It is also important to note that mathematical learning is a cumulative process and therefore a basic deficit in computation will have downstream effects: addition, subtraction and multiplication processes are involved in higher-level mathematics, such as geometry, algebra and calculus. In addition, high levels of anxiety are often associated with mathematics and these can pose obstacles to learning for children who find basic arithmetical tasks difficult (Ashcraft & Kirk, 2001). Individual differences in the manifestation of number problems have been reported in the cognitive–neuropsychological literature using a framework developed by McCloskey, Caramazza, and Basili (1985). Within this framework, the calculation system can be dissociated from the number processing system. Temple (1994) has reported single-case evidence for the existence in childhood of “digit dyslexia,” in which there is a specific difficulty in the acquisition of lexical processes within the number processing system (i.e., problems in encoding the meaning of numerals such as 34, 8483), “procedural dyscalculia,” in which there is difficulty in learning procedures and algorithms and “number fact dyscalculia,” in which there is specific difficulty in acquiring numerical facts. The manifestations of arithmetic difficulty depend on the age and stage of the child. Children with arithmetic difficulties initially experience problems with the count sequence, as they grow older they may tend to rely on the “count-on” strategy in simple addition for longer than typically developing children, albeit error-prone, and they have difficulty in learning number facts. With more complex addition problems, they tend to guess more and less accurately than their peers (Geary, Hoard, Byrd-Craven & DeSoto, 2004). Geary (1990) suggested that mathematically disabled children use the same strategies as agematched controls but differ in the speed and skill of strategy execution, they can retrieve fewer number facts, they are poor at monitoring their counting and they are poor at detecting computational errors (Geary, Bow-Thomas, & Yao, 1992). The incidence of mathematics difficulties is less well documented than for reading difficulties. In the UK, Lewis, Hitch, and Walker (1994) used a simple cut-off approach to defining difficulties among 9- to 10-year-old children and reported that only 1.3% of children showed a specific difficulty in maths Fig. 48.2 A two-dimensional model of the relationship between dyslexia and language impairment. [After Bishop & Snowling, 2004, with permission.] Risk of word-level reading deficit − Wider language, semantic & grammatical skills + Normal Reader Dyslexia Poor comprehender Language impaired poor reader + Phonological skills deficit comprehension reading Risk of 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 807

(standard score less than 85) in the presence of normal nonverbal ability and reading (at or above a standard score of 90 on both). However, another 2.3% had both reading and maths problems defined in an analogous way. This study reported an equal incidence of maths difficulties in boys and girls, in contrast to the higher incidence of reading difficulties among boys that they (and other studies) reported. Other large-scale studies have reported incidence rates of 6–7% for mathematics difficulties (Baker & Cantwell 1985; GrossTsur, Manor, & Shalev, 1996) while Share, Moffit, and Silva, (1988) using laxer criteria (a standard score of 92, the bottom 30% of the population) found combined rates of mathematics difficulties (with and without reading problems) of 11.2%. Given the different populations studied, and the different criteria for classification adopted, it is difficult to compare the rates reported. Nonetheless, it is clear that mathematical learning difficulties occur quite frequently and are often associated with reading difficulties. They also commonly co-occur with attention problems; Gross-Tsur, Manor, & Shalev, (1996) reported that 26% of children with mathematics disorder also had ADHD. Cognitive Explanations of Arithmetic Difficulties There is a relatively small literature investigating the cognitive impairments associated with mathematical difficulty in children who do not have comorbid reading impairments. Most of the evidence comes from arithmetic tasks (rather than mathematical problem-solving) and is therefore limited. Deficits in Number Processing Dehaene (1997) has argued that the basis of numerical cognition is a “number sense” – a preverbal system involving the ability to understand physical magnitudes and numerical quantities. It is possible that many of the problems observed in children with mathematics difficulties stem from a basic impairment in a number sense system that develops early and forms the foundation for later acquired verbally mediated mathematical skills (such as addition; Geary, 1993). In line with this, Geary, Hoard, and Hamson (1999) found that children with arithmetic problems were less accurate than controls at comparing the magnitudes of Arabic digits. Landerl, Bevan, & Butterworth, (2004) found that children with arithmetic difficulties, either alone or comorbid with reading difficulties, were slower than controls at number naming, number reading, number comparisons and verbal counting. Thus, basic number processing has been shown to be impaired in children with specific arithmetic difficulties, and is to some degree independent of other abilities (Dehaene, 1997; Gelman & Butterworth, 2005). In children with intact number sense, other cognitive resources that are used in mathematics seem to be deficient. Working Memory and Speed of Processing Impairments During calculation, subcomponents of an arithmetic problem must be held in temporary storage while processing proceeds. With multidigit problems, it is necessary to monitor the calculation process, to inhibit numbers from the initial calculation and to hold in mind the products of different steps in the calculation. Thus, arithmetic skills carry both simple and complex working memory demands and also tap executive function. It is therefore not surprising that working memory deficits are associated with arithmetic difficulties. Children with arithmetic difficulties perform poorly on complex working memory tasks, such as backward digit span (which has an executive component) and counting span (Geary, Hoard, & Hamson, 1999; Hitch & McAuley, 1991; Passolunghi & Siegal, 2001) but not typically on simple tests of verbal shortterm or phonological memory unless the task has a numerical component (Geary, Brown, & Samaranayake, 1991; Hitch & McAuley, 1991). According to Kail (1991), the amount of information that can be retained in memory depends on speed of processing, which in turn is related to the amount of attentional resources that can be directed to different tasks (Case, 1985). Bull and Johnston (1997) found that processing speed accounted for unique variance in arithmetic ability among 7-year-old children after controlling for differences in reading ability; children with lower arithmetic ability were slower than controls at number naming and sequencing, number matching, pegboard speed, one-syllable speech rate and reciting the alphabet. However, no IQ data were provided, and therefore processing speed may have been a proxy for general ability. Durand, Hulme, Larkin, and Snowling (2005) found that speed of information processing (as assessed by speed of visual search) was not a unique predictor of arithmetic skill after the effects of IQ and the speed of number comparison had been accounted for. This suggests that the speed of processing numerical information (rather than general information processing speed) may be critical for the development of arithmetic skills. Executive Deficits A body of evidence implicates executive deficits in arithmetic disability. McLean and Hitch (1999) found that 9-year-old children with specific arithmetic difficulties were impaired on the “Trail-Making” task where they were required to connect alternating sequences of numbers and letters (e.g., 1-A, 2-B) or numbers and colors (e.g., 1-yellow, 1-pink, 2-yellow, 2-pink). In a similar vein, Bull, Johnston, and Roy (1999) reported that children with high and low arithmetic ability differed on several aspects of the Wisconsin Card Sorting Test, notably perseveration (see also Bull & Scerif, 2001). The authors proposed that children with specific arithmetic difficulties have executive impairments that impair their ability to shift psychological set, plan action and judge the reasonableness of answers – all skills that are involved in mathematics. However, such difficulties may be attributable to comorbidities with other disorders (e.g., ADHD) that have not been controlled for in these studies. Spatial Deficits There is good evidence for associations between mathematical and spatial abilities (Dehaene, 1997; Hermelin & O’Connor, CHAPTER 48 808 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 808

1986). It is also common for children with non-verbal learning difficulties (typically associated with deficits on tests of spatial ability and performance IQ) to show mathematical difficulties (but not necessarily problems with number facts that are verbal). Such associations may reflect the anatomical proximity of brain systems subserving number sense and spatial processing. Alternatively, they may reflect a more fundamental association; the number sense system is itself a spatial system involving a spatially arranged “number line” (Dehaene, 1997). More basically, dealing with place values in arithmetic requires that we keep track of the spatial arrangements of numbers. Verbal Impairments Some aspects of arithmetic involve verbal skills. Learning to count is a verbal skill and problems with learning the count sequence are common in children with mathematics disorder. Similarly, arithmetic problems may place heavy demands on verbal working memory systems and these in turn place heavy demands on phonological (speech-based) coding. The frequent co-occurrence of reading and mathematics difficulties indicates that many children with mathematics difficulties will have phonological problems, and such problems might well be expected to compromise learning to count and the manipulation of numerical information in verbal working memory tasks. To summarize, the nature of mathematics difficulties is much less well understood than reading difficulties, and this reflects the fact that much less is understood about the mechanisms of mathematic skills and their development than for reading skills and their development. Mathematical skills depend upon a complex interplay between non-verbal and verbal cognitive systems, and mathematical skills are arguably more diverse and more complex than reading skills. It seems likely from a cognitive perspective that mathematical difficulties may result from a number of underlying deficits, including deficits in a non-verbal “number sense” system located in parietal brain areas as well as verbal systems that interact with this system. Further progress in this area is likely to depend upon longitudinal studies that attempt to focus on more welldefined arithmetical skills. Etiology Genetic Effects There is evidence indicating substantial genetic and environmental influences on the development of mathematical skills generally, and more specifically on the development of mathematics difficulties. There is good evidence that mathematical difficulties tend to run in families but this may reflect either shared environment or genetic effects. In a large-scale UK twin study, Kovas, Harlaar, Petrill, and Plomin (2005) found evidence for substantial heritability for normal variations in mathematical skills. There were substantial overlaps between the genes responsible for arithmetic and general intelligence, and arithmetic and reading, although the degree of overlap was far from perfect, suggesting that there are specific genetic effects on the development of arithmetic skills. There are very few studies that have directly assessed possible genetic influences on mathematical difficulties (as opposed to normal variations in mathematical skills). In a study with a large sample size (Oliver, Harlaar, Hayiou-Thomas et al., 2004), the heritability of mathematical difficulties was assessed by selecting children in the bottom 15% of the population on teacher ratings of children’s mathematical abilities. This study yielded a high group heritability estimate for mathematical difficulties of 0.65 (compared to the estimate of 0.38 reported by Alarcón, DeFries, Light, & Pennington, 1997, based on a smaller sample). These results are compatible with the same genetic influences operating to produce the group deficits in mathematics as well as the range of individual differences in mathematical skills observed within the population as a whole (Plomin & Kovas, 2005). In summary, current evidence suggests that there are substantial genetic influences on mathematical difficulties and that these same genetic influences may also operate to influence individual differences among people in the normal range of mathematical ability. It has also been reported that the comorbidity between mathematical and reading difficulties is in part brought about by common genetic influences operating on both disorders (Knopik, Alarcón, & DeFries, 1997). Brain Bases of Arithmetic Disorders Neuroscientific studies suggest that the neural substrate of the number sense system depends critically upon bilateral areas of the horizontal intraparietal sulcus (HIPS) (Dehaene & Cohen, 1997). Dehaene, Piazza, Pinel, and Cohen (2003) have proposed that there are three parietal circuits for numerical processing. Problems in the development of such brain systems may be fundamental to the problems observed in children with mathematical difficulties, although as yet direct evidence for this is lacking (Wilson & Dehaene, 2006). Consistent with the idea of mathematical difficulties being associated with parietal dysfunction, Isaacs, Edmonds, Lucas, and Gadian (2001) reported a specific reduction in gray matter in the left HIPS in a group of adolescents with mathematical difficulties (without reading problems) who had been born prematurely, compared with a control group without mathematical difficulties who had been born equally prematurely. This difference in the left HIPS was only found for children with problems with calculation, and not for another group of children who had problems with mathematical reasoning. Also, several studies have shown parietal deficits in Turner’s syndrome, a syndrome associated with arithmetic deficits (Reiss, Mazzocco, Greenlaw, Freund, & Ross, 1995). Developmental Co-ordination Disorder Nature, Classification and Incidence Developmental co-ordination disorder (sometimes referred to as “dyspraxia”) is a disorder of motor skills and is included here because problems with motor skills can adversely affect children’s educational achievements and self-esteem. Formally, READING AND OTHER SPECIFIC LEARNING DIFFICULTIES 809 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 809

the diagnosis of developmental co-ordination disorder (DCD) is used to describe problems of motor co-ordination that occur in otherwise normal children and significantly affect the activities of daily living. In practice, such problems often signify risk factors for other disorders, and DCD is commonly found in association with developmental disorders such as language impairment (Hill, 2001) or autism, and the overlap with attention problems is high (Gillberg, 1999). Population estimates of the incidence of DCD vary widely (5–18%) and these estimates depend both on the tests and the cut-offs used for diagnosis (Geuze, Jongmans, Schoemaker, & Sit-Englesman, 2001). Arguably, tests for the assessment of motor difficulties are less thoroughly developed and less well standardized than tests of reading, arithmetic and IQ but teacher and parent ratings are useful screening tools (Chambers & Sugden, 2006; Green, Bishop, Wilson et al., 2005). It has been reported that there is a ratio of at least two boys to each girl with DCD (Wright & Sugden, 1996), although data on sex ratios may be hard to interpret because some of the tasks used to assess motor skills are gender-biased (e.g., throwing a ball) and there is little agreement among professionals about how to diagnose DCD (Sugden & Chambers, 2005). The symptoms of DCD can vary considerably and may include gross motor difficulties, such as problems running, hopping, jumping, catching a ball and balancing, and fine motor difficulties including a lack of manual dexterity, difficulty in doing up buttons and laces, in dressing and in using eating utensils. Speech-motor skills can be affected and problems of pencil control are widespread. When DCD occurs in pure form, such children have been reported to have normal reading skills and only minor spelling problems (Lord & Hulme, 1987a) even though their handwriting is usually very poor. A mistaken view is that children with DCD grow out of their clumsiness; follow-up studies are rare but evidence suggests that such children remain less physically competent throughout adolescence (Gillberg, Gillberg, & Groth, 1989) and the difficulties they have at secondary school include problems with handwriting and the presentation of work, and difficulties in science, art, design and technology (Losse, Henderson, Elliman et al., 1991). However, the coupling between motor impairments and academic achievement may not be causal and is likely mediated by comorbidities and/or psychosocial problems. Explanations of Developmental Co-ordination Disorder A dominant approach to explaining the motor deficits found in children with DCD has been in terms of perceptual impairments, particularly in terms of problems with kinesthetic or visual perception. (An earlier term used to refer to this group of children was developmental apraxia and agnosia which captures the central role of perceptual disorders in the clinical profile of these children.) Problems of Kinesthetic Perception Kinesthesis refers to an awareness of the position, location and velocity of movement of the limbs and the forces exerted by the muscles. Poor kinesthetic sensitivity has been reported among children with DCD (Laszlo, Bairstow, & Bartripp, 1988) but this finding has not been widely replicated (Lord & Hulme, 1987b) and a meta-analysis found only a weak association between kinesthetic sensitivity and poor motor skills (Wilson & McKenzie, 1998). Visual Perceptual Deficits Stronger evidence exists for an association between visual perceptual problems and motor disorders (in the absence of problems with visual acuity; Henderson, Barnett, & Henderson, 1994; Lord & Hulme, 1987a), with the greatest deficiency being observed in visuospatial tasks, regardless of whether they have a motor component. It has been proposed that guidance of our movements in space depends upon a sensorimotor map that serves to translate visually perceived locations to spatially appropriate action patterns (Held & Hein, 1963). It could be argued that a deficit in the visual perception of spatial information will inevitably lead to problems in the guidance of movements and problems in “calibrating” and “recalibrating” the sensorimotor map during development. Clinically, occupational therapists often use visual perceptual training programs with these children (Cermak & Larkin, 2002). Balance and Postural Control More proximal causes of DCD have been proposed in balance and postural control, movement planning and preparation, and execution and feedback processes (Geuze, 2005). In addition, limitations of memory and attention and reduced muscle strength may have a role to play. It should be noted that in principle some of these difficulties might arise as a consequence of the perceptual impairments discussed above. Etiology There is evidence that low birth weight or prematurity increases the risk of developing the disorder (Jongmans, Demetre, Dubowitz, & Henderson, 1996; Marlow, Roberts, & Cooke, 1989), suggesting links with neurodevelopmental immaturity. Furthermore, as noted in ICD-10 (WHO, 1996), a careful clinical examination may reveal neurological symptoms such as choreiform movements of unsupported limbs in such children. More generally, the comorbidity of DCD with impairments of reading and language, as well as with ADHD and autism spectrum disorder suggests shared genetic risk with these other developmental disorders (see chapter 3; Chambers & Sugden, 2006). A recent behavioral genetic study using questionnaire-based measures of DCD and ADHD with a large sample of twins (Martin, Piek, & Hay, 2006) indicates a substantial heritable influence on each disorder, as well as a substantial shared genetic influence. Non-verbal Learning Disabilities Definition A diagnosis of non-verbal learning disabilities (NLD) is sometimes given to a child who displays difficulties with CHAPTER 48 810 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 810

READING AND OTHER SPECIFIC LEARNING DIFFICULTIES 811 visual-perceptual-organizational abilities, motor skills, tactile perception, and non-verbal problem-solving in the absence of basic decoding or spelling impairments (Rourke, 1989, 1995). However, non-verbal learning difficulty syndrome is not a disorder with validated clinical criteria and therefore the diagnosis is controversial; rather it cuts across taxonomies such as reading and mathematical disorders that classify children according to patterns of impairment in the academic arena. Although described as a non-verbal difficulty, many children with NLD experience speech-language difficulties including pragmatic deficits (Semrud-Clikeman & Hynd, 1990). Worling, Humphries, and Tannock (1999) reported that children with NLD had difficulties making inferences despite apparently good verbal skills, and Klin, Volkmar, Sparrow, Cicchetti, and Rourke (1995) found a strikingly high degree of concordance between Asperger’s syndrome and NLD but not between NLD and high-functioning autism. Cognitive Deficits in Non-verbal Learning Disabilities Most studies of NLD involve clinical samples and epidemiological data are not available. Moreover, few research studies have included adequate control groups and findings regarding the cognitive deficits in NLD are often tautological in that they reflect diagnostic or recruitment criteria. For example, although it is possible that deficits in spatial cognition are at the core of the syndrome, it must be remembered that the diagnosis may have been given to children who in particular gain lower performance than verbal IQs. Similar criticisms can be leveled at studies that test Rourke’s (1995) hypothesis that the primary deficits are in visual and tactile perception, dealing with novel stimuli, and analogical reasoning (e.g., Chow & Skuy, 1999; Cornoldi, Dalla Vecchia, & Tressoldi, 1995). It seems likely that, as theoretical understanding of the different components of NLD and their cognitive causes improves, the syndrome will be reconceptualized. At the present time, positing an overarching syndrome of NLD has little value and it is more productive clinically to assess and treat the diverse problems that are brought together under this heading. Emotional and Behavioral Adjustment in Learning Difficulties Reading Difficulties There is evidence of a link between reading difficulties and both disruptive behavior (Hinshaw, 1992; Maughan, Pickles, Hagell, Rutter, & Yule, 1996) and emotional disorders (Maughan, Rowe, Loeber, & Stouthamer-Loeber, 2003; Willcutt & Pennington, 2000). However, the processes responsible for these outcomes are not understood. An influential hypothesis has been that behavior problems associated with reading difficulties may result from progressive school failure and lowered self-esteem (Chapman & Tunmer, 1997). An alternative causal model of the relationship is that disruptive behavior at school is the result of attention problems which are comorbid with poor reading and may interfere with the acquisition of reading skills. However, the causal relationships between reading, behavior and emotion are complex, and may differ between boys and girls and depend upon the stage of development that is considered (Williams & McGee, 1994). In a study of 289 9- to 15-year-olds identified as having specific literacy difficulties from a representative sample of some 5000 UK children, Carroll, Maughan, Goodman, and Meltzer (2005) reported that children with reading difficulties are at increased risk of attention problems, conduct disorder, anxiety disorders and depressed mood. However, they argued that the mediating mechanisms differ. The association between literacy difficulties and behavior problems was mediated by inattention (rather than hyperactivity), whereas the link with heightened levels of anxiety was direct. A similar conclusion was reached from a twin study of literacy difficulties by Willcutt and Pennington (2000). These investigators reported an increased risk of attention and conduct difficulties in probands as well as cotwins; however, anxiety was reported only in those with reading difficulties, suggesting that such difficulties may arise as the result of stresses associated with educational difficulties. Regarding the link between poor reading and low mood, Willcutt and Pennington (2000) reported heightened levels of depression in girls mediated by ADHD, whereas Carroll, Snowling, Hulme et al. (2003) found that self-reported low mood was more common in boys than girls, and primarily in the 11- to 12-year-old age group. Longitudinal data are required to test hypotheses regarding the psychosocial sequelae of reading difficulties. Snowling, Muter, & Carroll, (2007) assessed the outcomes of children at family risk of dyslexia at 12 years. There was an elevated risk of attentional and emotional problems in those who had reading problems (according to parental report); however, the children rated themselves as positively as did normal readers, except in the academic arena. Maughan, Pickles, Hagell et al. (1996) followed 127 poor readers from the age of 10 years into early adulthood. There was a tendency for reading difficulties to be associated with poor attention and overactivity, which in turn placed poor readers at risk of behavior problems (see also Fergusson & Lynskey, 1997). However, behavior problems at 14 years reflected earlier behavior problems rather than reading difficulties, and social adversity was found to increase the risk of antisocial behavior among girls but not among boys (for whom increased rates of offending were associated with poor school attendance). As young adults, about 25% of this sample remained severely impaired in reading (Maughan & Hagell, 1996). Nonetheless, relatively positive self-reports suggested that many had gained employment in which there were restricted literacy demands and their reading problems were no longer of functional significance. In the majority of areas, those with a history of specific reading difficulties were functioning comparably to peers. However, young women with a history of specific reading retardation were at increased risk of psychiatric disorder, possibly related to a high rate of relationship breakdown. Male poor readers, in contrast, had more difficulty 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 811

CHAPTER 48 812 in gaining independence. However, these difficulties were the consequence of comorbid difficulties with peer relationships rather than reading problems. Other Learning Difficulties Relatively little attention has been paid to the outcomes of specific learning difficulties other than reading although there is evidence that anxiety specific to the subject at school increases with time among poor mathematicians and in turn affects maths attainments. A little evidence suggests that the psychosocial outcomes of children with developmental co-ordination disorder can be reasonably good with low self-esteem restricted to the motor domain (Losse, Henderson, Elliman et al., 1991), although poor social competence has also been reported. A frequent observation has been that rates of depression and suicidal behavior or ideation in adolescents and young adults with NLD are relatively high. However, studies suffer from the lack of representative samples and appropriate control groups (Little, 1993), and mediating mechanisms are unclear. In particular, the role of comorbid disorders in determining outcomes has not been addressed. In summary, although it is generally believed that specific learning difficulties can cause psychosocial problems, the evidence for this view is sparse. The literature suggests that the majority of children with specific difficulties in literacy, numeracy or motor skills are relatively free of mental health problems. The heightened susceptibility to psychiatric disorder reported for children with NLD may reflect its comorbid nature. Clinical Implications Assessment Children with specific learning difficulties will rarely be referred to child psychiatrists unless such difficulties have contributed to emotional or behavioral difficulties. However, it may be easy to miss a specific learning difficulty in a child with a mental health problem (particularly in a child referred for ADHD). Children’s Reading Difficulties If a referred child reports a failure to learn to read, has dyspraxic tendencies or is seriously underachieving, the most appropriate strategy is to refer this child to an agency within the school system for assessment. A comprehensive assessment should include assessment of general cognitive ability (IQ), single word reading and spelling, reading comprehension, expressive writing and number skills (the Wechsler scales provide tools for comprehensive assessment of these skills; WISC-IV, Wechsler, 2004; WIAT-II, Wechsler, 2005). The assessment will have more value if it proceeds to assess phonological skills and the reading strategies the child is currently using with a view to prescribing appropriate intervention. In addition, tests of speed of processing and working memory, and in-depth investigation of oral language skills may be appropriate (Snowling & Stackhouse, 2006). In the past such assessments were the domain of educational psychologists; however, now it is often a teacher with specialist qualifications who would undertake such assessments, replacing IQ testing with assessment of language and/or non-verbal reasoning. Other Learning Difficulties Given the substantial overlap between reading difficulties and difficulties with mathematics, an assessment of mathematical performance using standardized tests should ideally be part of a comprehensive literacy assessment. However, time constraints often preclude this and a regrettable fact is that most referrals are from parents or teachers who are more concerned with planning literacy rather than numeracy support. It can be difficult for clinicians to provide parents with the answer to the question foremost in their mind, “Is my child dyslexic?” Current diagnostic practice varies considerably, and although the term “dyslexia” is more widely accepted in educational circles than in the past, it may be used in a general sense to convey “reading difficulties with a phonological basis,” irrespective of IQ. It is also important for clinicians to be aware that the label dyslexia may be used differently by different agencies. As with all developmental disorders, clinicians need to emphasize to families the dimensional nature of dyslexia; it can vary from mild to severe, there may be individuals who show some but not all of the symptoms (likely in families with dyslexia) and the problems that the child experiences may change through development with compensation possible in favorable circumstances (Snowling & Maughan, 2006). A number of different practitioners, including physiotherapists, occupational therapists, specialist teachers and pediatricians, have a role in the assessment of DCD. It is generally agreed that such assessments should incorporate the evaluation of a range of movements as well as the impact of motor difficulties on everyday skills and psychosocial functioning. Individually administered tests of gross and fine motor skills, incorporating ball skills, manipulative skills and balance, are commonly used (Henderson & Sugden, 1992) and parent and teacher completed checklists and self-report questionnaires can be useful (Chambers & Sugden, 2006; Green, Bishop, Wilson et al., 2005). It is also recommended that prior to an intervention program, physical fitness should be assessed. Interventions At the time of writing, there are few randomized controlled trials evaluating educational interventions; however, calls have been made that these should become the “gold-standard” methodology for informing educational policy and practice (Torgerson & Torgerson, 2001). Children who have a family history of dyslexia or a history of speech-language difficulties are at high risk of reading difficulties, and motor delays appear to be part of an inherited form of dyslexia. If speech production deficits persist to school age, the likelihood of literacy problems is high. It is therefore important that such children receive appropriate 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 812

special units. In addition, information technologies have a lot to offer. Ideally, students with dyslexia should be taught to become fluent keyboard users, with special instruction in the use of a spell-checker. In addition, some children with dyslexia can use voice-recognition technology as an aid to written work. In formal assessments and examinations, people with dyslexia should normally be eligible for concessions. The most common arrangement is extra time in written examinations, and dispensation for spelling errors. If the student has particularly poor reading and writing skills, then they may be allowed someone to read the questions to them or an amanuensis. In contrast to what is known about how to teach wordlevel reading skills, far less is known about how to promote reading comprehension effectively (for review see Westby, 2004). A meta-analysis of reading comprehension interventions designed for typically developing children reported that the eight most effective methods for improving text comprehension were comprehension monitoring, co-operative learning, graphic/ semantic organizers for learning new vocabulary, story structure training, question answering, question generation, summarization and multiple strategy teaching (National Reading Panel, 2000). Also, the collaborative practice of speech and language therapists with teachers is likely to provide useful strategies for these children to learn. Maths Intervention Evidence regarding effective interventions for children’s mathematical difficulties is sparse. In the USA, there has been some limited evaluation of preschool programs for the prevention of mathematical difficulties (Starkey & Klein, 2000) and in the UK, evaluations of individualized programs of instruction for children with poor mathematical skills are in progress (Dowker, 2004). So far, to our knowledge, there are no studies that have investigated the effectiveness of interventions for older children who have developed mathematical difficulties. This is clearly an important area for further research. To date, the received view is that interventions are best targeted at specific arithmetic processes that are weak or impaired; however, there is as yet no evidence regarding specifically what works for which children. Interventions for Developmental Co-ordination Disorder Evidence regarding effective interventions for DCD is sparse (Mandich, Polatajko, Macnab, & Miller, 2001). Broadly speaking, there are two approaches to intervention for such children: process-oriented and task-oriented approaches (Sugden & Chambers, 2005; Wilson, 2005). Process-oriented approaches begin with an analysis of the underlying components of the task to be achieved and aim to train these processes. Examples include sensory integration methods and kinesthetic approaches but neither has met with much success when compared with control interventions. Task-oriented approaches are more functional and aim to teach skills that are deficient, for example, eating, dressing, ball catching or writing. Most practitioners aim to harness the support of parents and teachers READING AND OTHER SPECIFIC LEARNING DIFFICULTIES 813 support during the preschool period, including speech and language therapy, and, more generally, parental support with literacy can be helpful (Hewison, 1988). However, it is important to be mindful that many children with preschool speech and language impairments may make a good start in learning to read but fail later as the demands of reading increase. Careful monitoring of high-risk children is therefore advisable throughout the primary school years to ensure the effects of early interventions do not wash out. Reading Intervention Theoretical knowledge of the relationship between phonological skills and learning to read, and phonological deficits in dyslexia has led to the development of effective reading intervention programs that promote phonological skills in the context of reading (Brooks, 2002; National Reading Panel, 2000; Troia, 1999). For children with reading difficulties, such programs are best delivered by trained personnel who understand how to tune a program to a child’s specific needs. The main elements of such approaches (e.g., Hatcher, Hulme, & Ellis, 1994) include: • Training in letter knowledge; • Teaching concepts of print; • Training to manipulate the phonemes in words; • Applying letter and sound knowledge to word reading and writing (phonics); • Reading text; • Writing activities. Recently, the approach has been adapted for delivery by mainstream teachers to whole classes, and by teaching assistants to small groups (Hatcher, 2006). In a randomized controlled trial, the approach has been shown to be effective with reading gains of on average 0.23 standard score points per hour of intervention, an educationally significant improvement (Hatcher, Hulme, Miles et al., 2006). These findings converge with those of other research groups and have direct policy implications for the treatment of children with dyslexia in the school system (Torgesen, 2005). However, it is important to emphasize that children with dyslexia can respond very slowly even to the most effective of teaching approaches (Hindson, Byrne, Fielding-Barnsley et al., 2005). An important issue therefore is the problem of “treatment resistors” – those children who, despite highquality intervention, do not respond to teaching and continue to have persistent reading impairments (Torgesen, 2000). These “difficult to remediate” children tend to have the most severe phonological deficits (Vellutino, Scanlon, Sipay et al., 1996), are often socially disadvantaged and many experience emotional and behavioral difficulties. Because of the intractable nature of the disorder in some cases, some families turn to alternative or complementary therapies. The evidence base for the efficacy of such therapies is almost totally lacking (Muter, 2003). For children who do not respond to conventional treatments, the best advice at the present time is to consider more intensive therapies, including placement in 9781405145497_4_048.qxd 29/03/2008 02:54 PM Page 813

when implementing such programs. This is one way of circumventing a possible disadvantage of such approaches which is lack of transfer to related activities. Conclusions and Future Directions Understanding of the nature and causes of children’s reading difficulties is well advanced as is knowledge about appropriate interventions for word-level decoding difficulties. In this domain, cognitive models of reading acquisition have had a positive effect on progress. Although less is known about children’s arithmetic difficulties, the influence of cognitive models is beginning to bear fruit on methods of assessment and intervention. An advantage of the cognitive approach to learning difficulties is that it makes contact with what is know about normal development; furthermore, an understanding of the cognitive phenotype of disorders can foster understanding of links between genes, brain and behavior. 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820 Terminology and Definitions The terms used to refer to intellectual disability have undergone numerous changes over the last century. As terms used to describe socially devalued groups enter the common vocabulary, they quickly acquire disparaging connotations. Today’s scientific terminology quickly becomes tomorrow’s terms of abuse. “Idiots,” “imbeciles,” “morons,” “subnormals” and “retards” are nowadays nothing more than terms of denigration. In this chapter we use the term intellectual disability in preference to the synonymous terms “mental retardation” (used in the ICD-10 and DSM-IV-TR classificatory systems) and “learning disability” (often used in the UK). Our choice reflects intellectual disability having become the preferred terminology within the international scientific community. It also has the value of avoiding confusion arising from the use of terms that have very different meanings in different countries (e.g., learning disability). The definition of intellectual disability involves two core components: a general deficit in cognitive functioning, which emerges during childhood (American Psychiatric Association, 2000; World Health Organization, 1996). A “general deficit in cognitive functioning” is usually operationalized as a score of less than 2 standard deviations (SD) below the mean on a standardized IQ test. (Given that most IQ tests are constructed to have a mean of 100 and standard deviation of 15, this is ordinarily equivalent to a score below 70.) However, intelligence is not a unitary construct. As such, individuals whose test performance places them within this range may have markedly different profiles across the wide range of cognitive skills and abilities that are assessed by IQ tests. The definition is important in discriminating between people with significant deficits in multiple areas of cognitive functioning and people with very specific cognitive deficits (or specific learning difficulties). The second component of the definition (emergence during childhood, typically before the age of 18) is important in distinguishing people with intellectual disability from people with cognitive deficits acquired in later life; in particular, deficits associated with dementia. A third component, deficit in adaptive behavior, is sometimes added to the definition although this is more controversial. First, classificatory systems differ in the extent to which such deficits are seen as an inherent characteristic of the deficit in cognitive functioning or as an independent characteristic whose presence needs to be determined for the classification to apply. For example, ICD-10 guidance suggests that “adaptive behavior is always impaired, but in protected social environments where support is available this impairment may not be at all obvious in subjects with mild mental retardation” (World Health Organization, 1996, p. 1, italics added). In contrast, adaptive behavior is considered as an independent criterion in the commonly used definition advocated by the American Association on Intellectual and Developmental Disabilities (AAIDD, formerly the American Association on Mental Retardation; AAMR). Second, at present there is no consensus on how such “impairments” or “deficits” in social functioning and/or adaptive behavior should be operationalized. Finally, a strong scientific case can be made for considering social functioning and adaptive behavior in terms of the conjunction between impairments in cognitive ability and prevailing social arrangements (rather than as a defining characteristic of intellectual disability). Such an approach is consistent with the World Health Organization’s International Classification of Functioning, Disability and Health (ICF; World Health Organization, 2001). The ICF represents an attempt to integrate medical and social models of disability by describing the interplay between changes or impairments in body functions or structures (e.g., intellectual ability) and the person’s potential capacity and actual performance in a range of activities in specific environmental, cultural and personal contexts. Domains of activity/participation considered under the ICF include: learning and applying knowledge; general tasks and demands; communication; movement; selfcare; domestic life; interpersonal interactions; major life areas such as participation in education and employment; community, social and civic life. Typology of Intellectual Disability Intellectual disability (ID) can be considered to comprise two distinct groups. The first represents the lower end of the normal distribution of intelligence in the population. As a consequence, this group predominantly comprises individuals Intellectual Disability 49 Stewart Einfeld and Eric Emerson 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 820 Rutter’s Child and Adolescent Psychiatry, 5th Edition, Edited by M. Rutter, D. V. M. Bishop D. S. Pine, S. Scott, J. Stevenson, E. Taylor and A. Thapar © 2008 Blackwell Publishing Limited. ISBN: 978-1-405-14549-7

These are mild (approximate IQ 50–70), moderate (35–50), severe (20–35) and profound (below 20). However, it is important to note that individuals can vary considerably in their attainments across different developmental domains, often reflecting varied degrees of brain impairment to different cortical areas. The following descriptions are derived from the ICD-10 Guide for Mental Retardation (World Health Organization, 1996) and Harris (2006) and describe functional abilities at the end of adolescence. More detailed descriptions of attainments at different functional levels are provided by standardized measures of adaptive behavior, such as the Vineland Adaptive Behavior Scales (Sparrow, Balla, & Cicchetti, 1984). Individuals with mild ID typically have impaired literacy but normal language. There may be some emotional and social immaturity. Some young people with mild ID will develop a capacity for open or partially supported employment, albeit with unsophisticated task roles. They may marry and have children. However, as adults, rates of employment and independent living away from the family are lower in those with mild ID than in the general community (Hall, Strydom, Richards et al., 2005; Maughan, Collishaw, & Pickles, 1999). Those with moderate ID typically have impaired language. For example, Carr (2000) found that a cohort of adults with Down syndrome, with a mean IQ in the moderate range, had on average language development at the 5-year level. Basic selfcare skills are achieved. Social relationships such as friendships can be well developed. As adults, such individuals can eventually work productively in a special workplace setting with structured tasks and supervision. Fully independent living, marriage and parenting are very unusual. In severe ID, language may be absent or limited to individual words or phrases, or a limited range of signs may be used in communication. Elementary self-care may be achieved but assistance is usually needed with most basic living activities. Mobility may be normal. Daytime recreational activity programs are usual rather than work placement (Tesio, Valsecchi, Sala, Guzzon, & Battaglia, 2002). Profound ID is often a consequence of catastrophic brain damage, with multisensory and major motor impairments accompanying limited cortical cerebral function. Some comprehension of basic commands is attainable. Assistance, often through nursing care, may be required for nearly all activities. Incidence and Prevalence of Intellectual Disability Most epidemiological studies of ID have sought to estimate prevalence rates – the total number of cases existing in a population at a given point in time (Roeleveld, Zielhuis, & Gabreels, 1997). These studies typically use IQ assessments (see chapter 21) to classify a person as having either mild (IQ 50 or 55–70) or severe (IQ <50 or 55) ID, rather than a combination of IQ and adaptive behavior. In high-income countries in North America, Europe and Australia, studies have produced broadly consistent overall INTELLECTUAL DISABILITY 821 with mild ID with little evidence of identifiable brain disorder. ID is presumed to result from both genetic and environmental influences. There is a strong correlation between the intellectual function of the child and that of first-degree relatives (Bundey, Thake, & Todd, 1989). The heritability of ID in this group is about 0.5 (Spinath, Harlaar, Ronald, & Plomin, 2004). Genetic influences are presumed to be polygenic, although some specific gene loci have recently been identified as influential (Butcher, Meaburn, Knight et al., 2005). Fertility in this group is normal or near-normal (Maughan, Collishaw, & Pickles, 1999), as is life expectancy (Patja, Iivanainen, Vesala, Oksanen, & Ruoppila, 2000). There is a strong association with lower socioeconomic status (see p. 822; Birch, Richardson, Baird, Horobin, & Illsley, 1970). That this association is at least partly mediated by environmental effects is apparent from the results of adoptee studies (Capron & Duyme, 1989). General health is usually unimpaired. Adaptive function and adult capacity to work and live independently are relatively mildly impaired. The second group comprises ID as a consequence of identifiable or apparent brain disorders, of genetic or environmental origin (see p. 823). In this group, ID is typically more severe. There are more comorbid neurological problems such as epilepsy, and sensory or motor deficits, evidence of the greater degree of brain impairment. In this group, overt brain pathology is evident postmortem in most cases (Crome & Stern, 1972). Given that the majority of individuals in this group have a sporadic cause for ID, there is little or no correlation between the intellectual level of the affected child and their siblings or parents (Simonoff, Bolton, & Rutter, 1996). Stereotypic behaviors including self-injury and autistic symptoms are common (Einfeld, Piccinin, Mackinnon et al., 2006). In the developed world, there is also little or no correlation with socioeconomic status (Roeleveld, Zielhuis, & Gabreels, 1997). Fertility is regarded as substantially reduced and life expectancy is significantly lower than that of the community (Lavin, Mcguire, & Hogan, 2006). Given the more severe intellectual impairment, eventual adaptive capacity to fill normal adult roles is substantially more impaired. However, there are several important caveats to this typology. First, a minority of individuals with mild ID have identifiable causes. These may include acquired brain injuries, (e.g., from infection or trauma) or genetic disorders such as Prader–Willi or velocardiofacial syndromes (see p. 825). Second, a minor proportion of more severe ID will represent the group more than 3 SD below the mean on the normal distribution for intelligence. Third, it is important to recognize that there is substantial variation in level of function within each of these broad groupings. Functional Levels of Intellectual Disability Four levels of severity of ID, defined by ranges on standardized IQ tests, are described by both the ICD-10 and the DSM-IV. 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 821

prevalence rates for severe ID of 3–4 per 1000 of the general population, although studies that have screened entire populations tend to yield slightly higher prevalence rates (approximately 6 people with severe ID per 1000; Roeleveld, Zielhuis, & Gabreels, 1997). Studies that have sought to ascertain the prevalence of mild ID have reported much more diverse prevalence rates. This is likely to reflect at least two factors. First, most adults with mild ID do not use specialist services for people with ID. As a result, prevalence studies based on administratively defined adult populations will significantly underestimate prevalence rates of mild ID. Second, given that there is a strong association between socioeconomic deprivation and the prevalence of mild ID (see below), the level of socioeconomic deprivation in the communities sampled would be expected to have an impact on ascertained prevalence rates for mild ID. Studies that have screened entire populations have yielded prevalence rates of 25–80 people with mild ID per 1000 general population (Roeleveld, Zielhuis, & Gabreels, 1997; Simonoff, Pickles, Chadwick et al., 2006). Few studies have sought to ascertain the incidence of ID (the number of new cases arising in a population in a given period of time). A US study reported a cumulative incidence at age 8 years of 4.9 children with severe learning disabilities per 1000 births and 4.3 children with mild ID per 1000 births (Katusic, Colligan, Beard et al., 1996). Similar rates have been reported in Northern European research (Rantakallio & von Wendt, 1986). The low incidence of mild ID reported in these studies is likely to reflect the reliance on biased, administratively defined (rather than “true” population-based) samples of people with ID. There is no reliable information available on the global distribution of ID (Institute of Medicine, 2001). There is reason to believe that the incidence of severe ID in low-income countries is at least double that in high-income countries (Durkin, 2002). It has been estimated that the impact of undernutrition (as evidenced by severe to moderate stunting) alone may be responsible for a 31–43% elevation in the incidence of ID during childhood in low-income countries (Emerson, Fujiura, & Hatton, 2007). The prevalence and incidence of ID vary according to gender, age, ethnicity and socioeconomic circumstances. Gender Most studies report that males are more likely than females to have both severe ID (average male : female ratio 1.2:1) and mild ID (average male : female ratio 1.6:1), although gender ratios vary widely across studies (Roeleveld, Zielhuis, & Gabreels, 1997). It has been suggested that sex-linked genetic factors (Partington, Mowat, Einfeld, Tonge, & Turner, 2000), male vulnerability to insult and social processes in labeling and classification partly account for the majority of males with ID (Roeleveld, Zielhuis, & Gabreels, 1997). The latter are likely to be particularly relevant in studies that have relied on administratively defined populations of people with ID. Age Estimates of age-specific prevalence rates are highly influenced by methods of case identification (e.g., population screening versus the use of administrative samples). Most studies have reported an increase in the prevalence of both severe and mild ID throughout childhood, with prevalence peaking at 10–20 years of age (Roeleveld, Zielhuis, & Gabreels, 1997). While this may be because of the increasing “visibility” of ID in later school years, there is also evidence of IQ decline in some disorders. For example, Fisch, Simensen, and Schroer (2002) found evidence of declining IQ scores in children with fragile X syndrome, and this decline was greater than in children with autism. Ethnicity Estimating the impact of ethnicity on the prevalence and incidence of ID is difficult as other important factors also vary among ethnic groups. These include poverty, access to health care, lifestyles, communication barriers and uptake of specialist services (Modood, Berthoud, Lakey et al., 1997). However, research in the USA, UK and Australia has found tentative evidence to suggest higher prevalence rates of mild ID amongst some minority ethnic groups, such as African-American groups in the USA (Fujiura & Yamaki, 1997) and Aboriginal groups in Australia (Leonard, Petterson, De Klerk et al., 2005). In the UK, higher prevalence rates in South Asian communities have been reported for children and young adults with severe ID (Hatton & Emerson, 2004). However, it is unclear whether these higher rates are biologically or genetically linked with ethnicity (e.g., as a result of consanguinity), or are the result of other factors that have an impact upon minority ethnic groups, such as socioeconomic status or classification practices (e.g., through the use of culturally biased assessment methods). Socioeconomic Circumstances There is a strong association between lower socioeconomic position and higher prevalence rates of mild, but probably not severe, ID (Hatton & Emerson, 2004; Leonard, Petterson, De Klerk et al., 2005; Roeleveld, Zielhuis, & Gabreels, 1997). For example, children in the most socioeconomically disadvantaged 10% of Western Australian families had more than five times the risk of mild and moder-ate ID when compared with those in the least disadvantaged 10% (Leonard, Petterson, De Klerk et al., 2005). In Britain, children in the most socioeconomically disadvantaged 20% of families had more than four times the risk of ID when compared with those in the least disadvantaged 20% (Emerson, Graham, & Hatton, 2006). These associations have also been reported in middle- and low-income countries (Durkin, 2002). Possible changes in Prevalence The prevalence and incidence of ID are likely to change over time as a result of complex changes in society and the provision of education, health and social care. In high-income countries, factors that are likely to lead to an increase in the incidence of ID include: increases in maternal age (associated with higher risk factors for some conditions associated with CHAPTER 49 822 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 822

ID, such as Down syndrome); increased survival of “at risk” infants, such as very low birth weight infants or very preterm deliveries; increasing levels of HIV and AIDS in children; and increased rates of assisted conception. Factors that are likely to lead to a decrease in incidence include: increasing availability of prenatal screening for Down syndrome; improving health care and support resulting in fewer “at risk” infants developing ID. The net effect of these competing pressures on the overall incidence of ID is not known. However, there is a perception among practitioners that the rate of profound ID may have increased significantly over the past decade. Social and Health Impact of Intellectual Disability The social impact of ID can be considered at the level of the individual, their relatives and the wider society. As children, and later as adults, people with both mild and more severe ID are at significantly increased risk of facing discrimination, social exclusion and abuse (Department of Health, 2001; Grant, Goward, Richardson, & Ramcharan, 2005). In England, only 44% of the 95,000 children with a Statement of Special Educational Need for ID are educated in mainstream schools, a percentage that drops to just 20% for children with severe ID (Department for Education and Skills, 2005). As adults, people with both mild and severe ID are significantly less likely than their non-disabled peers to move out of their family home, have long-term intimate relationships, be employed, have friends and participate in the life of their communities (Emerson, Malam, Davies, & Spencer, 2005; Maughan, Collishaw, & Pickles, 1999). These trends toward extensive social exclusion appear to transcend national boundaries (Emerson, Fujiura, & Hatton, 2007) and be particularly exacerbated in people with more severe ID (Emerson, Malam, Davies et al., 2005). There is also extensive evidence that mothers (and to a much lesser extent fathers) of children with ID are more likely to shows signs of psychological distress and have lower well-being than parents of “typically developing” children (Baker, Blacher, Kopp, & Kraemer, 1997; Blacher & Baker, 2002; Blacher & Mink, 2004; Emerson, 2003). In addition to the health burden imposed on a vulnerable subgroup of parents, these findings are of concern as distress among mothers has been linked to a wide range of adverse outcomes for children, including less than optimal parenting, failure to engage with services, decisions to seek out-of-home care for their disabled child, impeded child development, and higher rates of child psychopathology and antisocial behavior (Llewellyn, McConnell, Thompson, & Whybrow, 2005; Zahn-Waxler, Duggal, & Gruber, 2002). Marriages in families with children with ID are only a little more likely to end in divorce (Risdal & Singer, 2004). It is perhaps surprising that severity of ID per se is not the major determinant of family stress (Baker, McIntyre, Blacher et al., 2003). The response of families to the presence of a chronically ill or disabled child is partly determined by parents’ ways of thinking about the child. There is evidence that mothers with a high sense of locus of control and a belief in chance feel less burdened by caregiving than those with the opposite cognitive set (Green, 2004). Other factors predicting high levels of stress for parents are increased rate of psychopathology among children with ID (Baker, McIntyre, Blacher et al., 2003; Eisenhower, Baker, & Blacher, 2005; Emerson, 2003; Hastings & Beck, 2004; Tonge & Einfeld, 2003) and the poorer socioeconomic circumstances of families supporting children with ID (Emerson, 2003; Emerson, Hatton, Blacher, Llewellyn, & Graham, 2006). Problematic or “challenging” behaviors are one of the main predictors of whether parents will seek a residential placement for their son or daughter (Llewellyn, Dunn, Fante, Turnbull, & Grace, 1999; Llewellyn, McConnell, Thompson et al., 2005). Daily care requirements on account of lack of mobility and incontinence of children with ID are also burdensome for parents, but do not cause as much stress in parents as behavior problems (Tonge & Einfeld, 2003). Siblings of children with ID in general do not show increased levels of distress or other psychopathology. There is some evidence that such siblings have more secure attachment styles and higher levels of emotional maturity (Levy-Wasser & Katz, 2004). At the clinical level, there is wide variation in the way families respond to the experience of having a child or sibling with ID. One approach that is helpful in counseling such families is to support effective grieving for the loss of the wishedfor healthy child. Families who are not unduly burdened by anger, guilt, shame or sadness are best able to have a realistic appreciation of their disabled child. In such families, the child with the disability is given the same value as other family members. Where this is not achieved, scapegoating of the affected child at one extreme, or overenmeshment with the disabled child at the other extreme is sometimes seen. In such families, “survivor guilt” may be apparent in siblings. There is evidence that parental stress can be ameliorated by group interventions. Tonge, Brereton, Kiomall et al. (2006) used a randomized control design in demonstrating that parent education and behavior management training, or parental counseling alone were effective in reducing parental distress in parents of children with autism. Hastings and Beck (2004) reviewed a range of controlled parent intervention studies and found most support for the effectiveness of cognitive–behavioral techniques in reducing parental stress, although effects were of small to medium size. The primary impact of ID on the wider society is financial. Current expenditure in England on health and social care services for people with ID is approximately £4 billion per annum (Association of Directors of Social Services, 2005). Increased rates of psychopathology among people with ID (see p. 827) also add major costs to care. Adolescents with ID who could gain vocational training through supported employment programs are unable to do so (Hupalo, 1997). Injuries to care workers are a major source of expense from compensation and occupational health and safety claims (Lowe, 1999) and the costs of supported accommodation INTELLECTUAL DISABILITY 823 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 823

services are significantly influenced by the extent of psychopathology exhibited by residents (Hallam & Emerson, 1999). Causes of Intellectual Disability Any pathogenic process that significantly impairs cognitive processing during childhood can cause ID. The most widely used classification of such causes is that of the AAIDD (Luckasson, Coulter, Polloway et al., 1992, Luckasson, Borthwick-Duffy, Buntinx et al., 2002). This groups causes into prenatal, perinatal and postnatal in origin. Prenatal causes include chromosome disorders, various dysmorphic syndrome disorders, inborn errors of metabolism and developmental disorders of brain formation, such as hydrocephalus or spina bifida, toxic and teratogenic influences such as fetal alcohol exposure and malnutrition. The second group, perinatal causes, includes placental insufficiency and neonatal disorders such as septicemia. Postnatal causes include head injuries, infections such as meningitis, and degenerative disorders such as the leukodystrophies, ID associated with seizures, toxic disorders such as lead poisoning, malnutrition and chronic social and sensory deprivation. In surveys of individuals with more severe ID (Curry, Stevenson, Aughton et al., 1997; Partington, Mowat, Einfeld et al., 2000), chromosomal abnormalities are identifiable in 20%, about three-quarters of whom have Down syndrome. Monogenic disorders, either autosomal or X-linked, account for about 3–4% each. Recognizable or provisional genetic syndromes are found in about a further 5%. Environmental causes have been estimated as responsible for about 8% of cases. The causal link in some of these cases is clearly apparent (e.g., herpes encephalitis in childhood). However, it is important to appreciate that some conditions apparent perinatally or postnatally have uncertain prenatal origins (Nelson, 2003). These include structural abnormalities of the central nervous system (5%) and complications of prematurity (5%). No cause is currently identifiable in 45–50%. There is reason to believe that the prevalence of severe ID in low-income countries is at least double that in highincome countries and that the distribution of causes is different (Durkin, 2002). Because of the lack of epidemiological studies it is not easy to distinguish cognitive impairments leading to specific learning disorders from those leading to ID. In low-income countries, undernutrition accounts for a larger proportion of at least mild ID (Olness, 2003). The most critical impact on brain development for undernutrition appears to be between the second trimester of pregnancy and age 2 years. Endemic iodine deficiency occurs in up to 10% of the population in some areas of the world, particularly parts of China, the Congo, South America and mountainous areas of South-East Asia (Olness, 2003). Deficiency in thyroid hormone during pregnancy or in the newborn period impairs development of cortical neurons and retards myelinization (Pharoah, Buttfield, & Hetzel, 1971). Infectious diseases continue to be prominent causes of ID in low-income countries. Important infections include tuberculous meningitis, hemophilias, influenza and type B meningitis. Given the failure to achieve widespread immunization, insect-borne viruses such as Western Nile virus, cerebral malaria and congenital human immunodeficiency virus infection are increasingly prevalent in lowincome countries and the brain impairment as a consequence has been documented (Drotar, Olness, Wiznitzer, et al., 1997). The wider use of antiviral agents to treat AIDS may result in large numbers of survivors with ID. Many conditions leading to cognitive impairment occur concurrently, increasing the risk for ID (Olness, 2003). For example, low-birth-weight babies may also have malnutrition and malaria. There is also some evidence to suggest that some genetic causes of developmental disabilities may also be unequally distributed (Institute of Medicine, 2001). For example, thalassemia, which is prevalent in 2–3% of all children in West Africa, has been linked to high rates of mild ID (Steen, Xiong, Mulhern, Langston, & Wang, 1999). In low-income countries, a higher proportion of births are to mothers aged over 35, possibly increasing the incidence of Down syndrome (Steen, Xiong, Mulhern et al., 1999). Finally, high rates of cosanguineous marriage have been associated with increased rates of child disabilities (Institute of Medicine, 2001; Teebi & El-Shanti, 2006). The causes of ID vary with the severity of intellectual impairment (see chapter 30). Down syndrome The genetic basis of Down syndrome is discussed in chapter 24; here we focus on the clinical characteristics. Down syndrome is the most common genetic cause of ID, occurring in approximately 1 in 800 live births. The risk for Down syndrome increases with increasing maternal age. Down syndrome is characterized by upturned outward slanting eyes, a wide nasal bridge, a large posterior fontanelle, a single transverse palmar crease and hypotonia. Congenital heart disease and duodenal atresia are common (Harris, 2006). Hearing impairments, hypothyroidism and atlantoaxial instability and an increased vulnerability to leukemia are also characteristic. Guidelines for the management of the general health of children with Down syndrome have been formulated by the Committee on Genetics (American Academy of Pediatrics Committee on Genetics, 2001). Severity of ID covers a broad range, but is most commonly moderate or severe. It is also associated with earlier onset of menopause in Down syndrome women (Schupf, Pang, Patel et al., 2003). Down syndrome is striking among genetic disorders causing ID in that it is associated with relatively low levels of psychopathology (Carr, 2002). There is some evidence to support the notion that children with Down syndrome have a stubborn temperament, but this is not problematic for most parents (Carr, 1994). Alzheimer-type dementia occurs at an increased rate and at an earlier age (mean of around 50 years) in Down syndrome. Early signs of dementia are a sustained increase in behavioral problems and a decline in independence and adaptive behavior skills (Carr, CHAPTER 49 824 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 824

2002). However, early dementia is occasionally apparent in young adulthood. Fragile X syndrome Fragile X syndrome (FXS) is caused by an expansion of the CGG trinucleotide sequence at Xq27.3 on the X chromosome (see chapter 24). Approximately one-third of boys with FXS have mild to moderate ID. One-third of carrier females have mild ID and the other two-thirds an IQ in the average range. The physical phenotype is characterized by a long face with protruding ears, a large jaw, hyperextensible joints and enlarged testes in postpubertal males (Hagerman, 1999). ID is usually mild to moderate and the degree correlates inversely to the level of fragile X mental retardation protein (FMRP) (Loesch, Huggins, & Hagerman, 2004). Verbal intelligence often exceeds performance abilities in both affected males and non-learning disabled female carriers. The IQ may decline in childhood and adolescence, with an average adult IQ in males at the low end of the moderate range. Approximately 70% of females with the full mutation have an IQ of less than 85. Verbal dyspraxia is common (Spinelli, Rocha, Giacheti, & Richieri-Costa, 1995). Children with FXS typically have initial social anxiety with aversion to eye contact, hand flapping and stereotypic behavior, but usually are socially responsive and affectionate with an interest in social interactions (Turk & Cornish, 1998). Self-injury, notably hand biting and scratching provoked by frustration, anxiety and excitement is common. Some children with FXS have autistic behaviors in childhood. Prader–Willi syndrome Prader–Willi syndrome has a prevalence of about 1 in 10,000– 15,000 live births. It results from the failure of the paternally imprinted genes in the region 15q11–q13 (see chapter 24). Physical characteristics of Prader–Willi syndrome include hypotonia and poor feeding in infancy followed by hyperphagia and consequent obesity and its cardiopulmonary complications from early childhood, hypogonadism and small hands and feet and short stature. There is a characteristic, although subtle, facial appearance. Most individuals with Prader–Willi syndrome function in the mild ID range, although a few have more severe ID impairment and some have average intelligence. Behavioral characteristics include marked hyperphagia, pica, gorging and stealing food. In addition, there are severe temper tantrums or episodes of rage. Insensitivity to pain, skinpicking or rectal gouging and impaired temperature regulation, hypersomnolence and reduced motor activity are also features (Einfeld, Smith, Durvasula, Florio, & Tonge, 1999b). Obsessional symptoms have also been noted (Dykens, 2004). There appears to be an increased vulnerability to psychosis in Prader–Willi syndrome. Although psychosis has been noted in both the deletion and uniparental disomy (UPD) forms, it is about six times more common in the UPD derived cases. There is evidence of hypothalamic disturbance from both postmortem and functional magnetic resonance imaging (fMRI) studies (Shapira, Lessig, He et al., 2005). Neither surgery nor medications have been found effective in managing the hyperphagia. Instead, strict control of food intake is necessary. Sometimes this requires locking cupboards or refrigerators to prevent access to food (Holland, Whittington, & Butler, 2002). Medical management of the complications of obesity is required. Behavioral difficulties continue into young adulthood, but there is evidence that they decline in the 4th and 5th decades (Dykens, 2004). Williams syndrome Williams syndrome is caused by a chromosome deletion at 7q11.23 (see chapter 24). Around 95% of children with the condition have the same deletion, but a few individuals have partial deletions. Williams syndrome is characterized by short stature; hypercalcemia in infancy and subsequent abnormal dentition; vascular abnormalities, particularly supervalvular aortic stenosis; a stellate pattern in the iris; atypical face, sometimes described as “elfin-like”; and ID, generally in the low/mild or upper moderate range. Psychometric testing usually identifies language function significantly better than visuospatial function (Howlin, Davies, & Udwin, 1998). Children with Williams syndrome show more noise sensitivity, sleep disturbance and anxiety than other children with ID (Einfeld, Tonge, & Rees, 2001). The anxiety pattern is quite distinct. Children with Williams syndrome have a high phobic anxiety but not social anxiety. Indeed, they have an absence of social anxiety. This has led to a substantial rate of sexual abuse of girls with Williams syndrome (Davies, Udwin, & Howlin, 1998; Dykens, 2003). Although the behavioral difficulties remain evident in young adulthood, they are less prominent (Tonge & Einfeld, 2003). Angelman syndrome Angelman syndrome involves a deficit in the same region on chromosome 15 as Prader–Willi syndrome. However, Angelman syndrome is caused by a deficit in the region inherited from the mother, whereas Prader–Willi syndrome is a consequence of a deficit in the same region inherited from the father (see chapter 24). Individuals with Angelman syndrome have a characteristic face with a wide mouth, a thin upper lip and a prominent tongue. The head is small. Most are fair with blue eyes. Feeding problems are common in the neonatal period. Children with Angelman syndrome have a characteristic ataxic gait with arms upheld and flexed. They have frequent laughing, which is mainly in response to social stimuli (Horsler & Oliver, 2006). Fascination for water, hand flapping, abnormal food-related behaviors and sleep disturbance occur more commonly than in IQ-matched controls (Barry, Leitner, Clarke, & Einfeld, 2005). Epilepsy is usual and often severe. ID is in the severe or profound range with little speech, although some affected children use a limited range of signs to communicate (Holland, Whittington, & Butler, 2002). Velocardiofacial Syndrome Velocardiofacial syndrome (VCFS) is a consequence of a deletion at 22q11.2 (see chapter 24). The physical phenotype INTELLECTUAL DISABILITY 825 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 825

includes congenital heart disease, cleft palate or other palatal anomalies, and a characteristic facial appearance including a long narrow face and a prominent nasal tip. Abnormalities of calcium metabolism and immune function are common. Individuals with VCFS often have mild ID but may have intelligence in the normal range. Particular difficulties with mathematics are common. As children, they are commonly shy and withdrawn with a bland affect. In adolescence or young adulthood, psychosis emerges in a high proportion of cases. In a large series, Murphy, Jones and Owen (1999) found a prevalence of psychosis of 30%, the majority of which was schizophrenia. At present, there is no known way of preventing the onset of psychosis. One series reported a poor response to antipsychotics (Gothelf & Lombroso, 2001), but another series suggested outcomes similar to schizophrenia in general (Murphy, 2005). Prevention of Intellectual Disability The prevention of ID raises a complex set of ethical issues (Louhiala, 2004). Least contentious among approaches to prevention are those that seek to avoid exposure to social and environmental risk factors for ID such as poverty, undernutrition, environmental toxins, infections, poor obstetric care, understimulating home environments, intrafamilial marriage, child abuse or low maternal education. It has been estimated, for example, that reducing the proportion of children living in poverty who are exposed to environmental deprivation could decrease the prevalence of ID in the USA by approximately 10% (McDermot & Altekrusse, 1994). Recently, the International Child Development Steering Group have reviewed the evidence relating to risk factors for adverse developmental outcomes for children in low and middle income economies (Engle, Black, Behrman et al., 2007; Walker, Wachs, Gardner et al., 2007). While not specifically related to ID, there is a clear overlap between risk factors for not attaining general developmental potential and risk factors for ID. They identified four key risk factors where existing evidence suggested that the need for intervention was “urgent” (stunting as a result of inadequate nutrition, inadequate cognitive stimulation, iodine deficiency and iron deficiency anemia) and five areas where sufficient evidence existed to “warrant intervention” (malaria, intrauterine growth restriction, maternal depression, exposure to violence, and exposure to heavy metals; Walker, Wachs, Gardner et al., 2007). They suggested that the most effective early child development programs “provide direct learning experiences to children and families, are targeted toward younger and disadvantaged children, are of longer duration, high quality, and high intensity, and are integrated with family support, health, nutrition, or educational systems and services” (Engle, Black, Behrman et al., 2007). Although there has been progress towards reduction of iodine deficiency in many countries, the WHO still estimates that in 2003, 36.5% of school-age children had insufficient iodine intake. Iodine deficiency actually increased in Europe between 1993 and 2003. Salt iodization continues to be an effective strategy (Andersson, Takkouche, Egli, Allen, & de Benoist, 2005). Folate supplementation reduces the rate of neural tube defects (Stoll, Alembik, & Dott, 2006). Lead poisoning can be prevented through screening children living near lead industries, the elimination of lead in petrol, old paint removal and replacement of lead water pipes. Some programs to reduce antenatal exposure to alcohol have been successful but others have been disappointing (Hankin, 2002). Reduction of head injuries through improved road safety and compulsory wearing of bicycle helmets and reductions in near-drowning morbidity are feasible. A number of studies have reported effective primary prevention programs to reduce injuries through child abuse, but secondary prevention to reduce repeat abuse has been less successful (Vandeven & Newton, 2006). Concerning genetic causes of ID, genetic counseling provides information to guide reproductive choice (see chapter 73). Reducing the rate of consanguineous marriages can be a target of public health education (Alwan & Modell, 2003). The best candidates for prenatal gene therapy have been studied for glycogen, lipid and mucopolysaccharide storage diseases. However, successful prenatal gene therapy has not yet been demonstrated successfully in animals and there are a number of bioethical concerns about developing technology that can potentially manipulate the human genome (Ye, Mitchell, Newman, & Batshaw, 2001). The contemporary rarity of once common causes such as congenital rubella and kernicterus demonstrate what can be achieved. Reduction of the prevalence of ID remains a viable goal. Health Complications of Intellectual Disability General Health People with ID are more likely to experience poor general health and have a decreased life expectancy (Ouellette-Kuntz, 2005). While much remains to be learned about the causes of these disparities in health outcomes, existing research has drawn attention to the potential importance of a number of factors including the impact on health of the genetic and biological bases of ID, for example, thyroid impairment and atlantoaxial instability in Down syndrome (Cohen, 2006; Dykens, 1999, 2000; Hodapp & Dykens, 2004); increased risk of exposure to socioeconomic disadvantage (Emerson & Hatton, 2007a,b), behavioral or lifestyle factors (Emerson, 2005b; Robertson, Emerson, Gregory et al., 2000); and the quality of existing health care support provided to people with ID (Webb & Rogers, 1999; Whitfield, Langan, & Russell, 1996). The evidence pertaining to the potential importance of socioeconomic, behavioral or lifestyle factors and the quality of health care support suggests that the health status of people with ID could be improved and that the disparity in health outcomes between people with ID and their non-disabled peers may be reduced (Department of Health, 2001; Disability Rights Commission, 2004; Einfeld, Smith, Durvasula et al., 1999b; Meijer, Carpenter, & Scholte, 2004; US Department of Health CHAPTER 49 826 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 826

cohort of children and adolescents with more severe ID and identified 40% of the children aged between 4 and 18 years as meeting criteria as a psychiatric case. In comparison, 14% of Australian children without ID in a random community sample were found to have a psychiatric disorder (Sawyer, Arney, Baghurst et al., 2001). In Britain, it has been estimated that 39% of 5- to 15-year-old children with ID had a diagnosable psychiatric disorder, compared to 8% among children without ID (Emerson, 2003). Major psychopathology affects over 40% of young people with ID (Einfeld & Tonge, 1996b), therefore the number of persons affected by ID and severe psychopathology is approximately equal to the number with schizophrenia. Factors Contributing to the High Prevalence of Psychopathology These may be grouped as biological, psychological and social risk factors. Biological factors include particular genetic causes of ID that lend vulnerability to particular syndromes of psychopathology. Einfeld, Tonge, Turner, Parmenter, and Smith (1999a) found that children with Prader–Willi and Williams syndromes had considerably higher levels of psychopathology than did children with FXS or an epidemiological control group. Those with Down syndrome had significantly lower levels than controls. Various concomitant brain impairments that may accompany ID may increase the risk of behavior disturbance, such as complex partial seizures, or frontal lobe damage causing impulsivity. Sensory impairments are frequent in children with ID, and these are known to increase the risk of psychopathology (Sisson, Van Hasselt, & Hersen, 1993). Psychological factors include the reduction in capacity for finding creative and adaptive solutions to life challenges. This is the corollary of the observation that children and adolescents of high intelligence have greater resilience to psychopathology (Goodman, 1995; Tiet, Bird, Davies et al., 1998). Family dysfunction and parental mental health problems are associated with increased psychopathology in children with ID (Wallander, Koot, & Dekker, 2006), but the direction of causality is unclear. Social disadvantage and poverty are an increased risk for children and adolescents with ID; social conditions that have been linked to risk of psychopathology (BMA Board of Science, 2006; Hatton & Emerson, 2004). They also experience higher rates of stressful life events, such as abuse, school failure and peer rejection, than children without ID (Ammerman, Hersen, van Hasselt, Lubetsky, & Sieck, 1994; Hatton & Emerson, 2004). It has been estimated that 20– 33% of the increased risk of psychopathology among children with mild ID can be attributed to the impact of social disadvantage mediated by an increased risk of exposure to a range of adverse life events (Emerson & Hatton, 2007b). Conceptual Issues and Classification of Psychopathology Historically, the concepts of ID and mental illness have had INTELLECTUAL DISABILITY 827 and Human Services, 2005). To the extent that the poorer health status of people with ID is avoidable and unjust, it can be considered to constitute an example of health inequity or inequality (Whitehead, 1992). Guidelines have been developed to guide health care practitioners in addressing the particular health needs of individuals with ID (e.g., monitoring thyroid status in individuals with Down syndrome; Beange, Lennox, & Parmenter, 1999). These have been developed in response to research showing high rates of undiagnosed common health problems in persons with ID. It is important to consider intercurrent or chronic physical ill health as potential causes of behavioral disturbances in those with ID. For example, esophageal reflux is a common covert cause of agitation and distress in children and adolescents with severe and profound ID. Epilepsy Around 30% of children with ID have epilepsy. The prevalence varies substantially between causes of ID. For example, those with Down syndrome have low levels of seizures, whereas for those with tuberous sclerosis or cerebral palsy, epilepsy is common. In some disorders (e.g., autism and FXS), epilepsy often begins for the first time in adolescence. Epilepsy can be associated with psychopathology in young people with ID in a number of ways. Complex partial seizure disorder (previously known as temporal lobe epilepsy) may manifest only with behavioral manifestations, such as undirected aggression or olfactory or dissociative phenomena. Second, anticonvulsants can have an impact on the behavior of children with ID (see chapter 30). In general, children with ID and seizures do not have higher rates of psychopathology than children with ID but without seizures (Lewis, Tonge, Mowat et al., 2000). Sensorimotor impairments Abnormalities of vision, hearing and motor function are common accompaniments of ID, but are often overlooked (Beckung, Steffenburg, & Uvebrant, 1997). Around 25% of children with idiopathic ID had visual impairments in one large study (Ghose & Chandra Sekhar, 1986). The prevalence of hearing impairment in children with ID is twice that found in typically developing children (Karjalainen, Kaariainen, & Vohlonen, 1983). Some conditions such as congenital rubella or severe anoxic brain injury can cause impairment of multiple senses. Psychopathology Psychopathology is a common and important feature of ID. Whereas methodological differences produce differing rates (for a review see Dykens, 2004), most studies find an increased rate two to four times that in the general population. The Isle of Wight studies of Rutter, Tizard, Yule, Graham, and Whitmore (1976) found that 7% of 10- to 12-year-old children in the community had psychiatric disorders, but for children with ID, the rate was 30%. Einfeld & Tonge (1996a,b) assessed psychopathology in an epidemiologically derived 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 827

CHAPTER 49 828 a confused relationship. Mental health professionals have tended to view emotional and behavioral disturbances in the presence of ID as a “behavioral” manifestation of ID, rather than evidence of mental illness. At the same time, disability advocates have been keen to distance ID from the perceived stigma and overly medicalized concept of mental illness (Einfeld, 1992). More recently, there has been an increasing awareness that psychopathology is distinct from, but can cooccur with ID. An exception to this would occur, for example, where a 14-year-old boy with a mental age of 2 years may have tantrums which are appropriate for his mental age, which nevertheless, because of the boy’s physical size, constitute a serious behavioral problem. Taxonometric or “bottom-up” models of psychopathology were examined by Aman (1991). He identified seven syndromes common to the factor analyses of several symptom-based inventories of psychopathology used in individuals with ID: aggressive/antisocial, social withdrawal, stereotypic behavior, hyperactivity, repetitive verbalization, anxious/tense/fearful and self-injurious. Standard DSM and ICD classifications are of limited value in individuals with the more severe levels of ID (Cooper, Melville, & Einfeld, 2003; Einfeld & Aman, 1995). Most specific diagnoses have not been subject to studies of interrater agreement. However, Einfeld, Tonge, Chapman et al. (2007) found the interrater agreement for the diagnoses of psychosis (any psychotic disorder) and depression (of any type) in a group of young people with ID to be high among clinicians who were trained in both psychiatry and ID. With the exception of autism, few diagnoses have had demonstrated concurrent, predictive or postdictive validity in individuals with more severe ID. Case reports and epidemiological studies suggest that the range of psychiatric syndromes seen in the general population also occur in the presence of ID (Emerson, 2003; Menolascino, Levitas, & Greiner, 1986). Some writers have identified a “pathoplastic” effect of cognitive impairment on symptoms (e.g., depression presenting with agitation or increase in stereotypic behavior; Smiley & Cooper, 2003). Children and adolescents with mild ID display psychopathology similar to that seen in others of the same mental age (Menolascino, 1971). The moderately and severely intellectually disabled are also subject to the psychiatric disorders seen in normal populations, albeit with modified symptoms, but also have a range of symptoms that are uncommon or rare in those without ID (Quine, 1986). Of those psychiatric problems that are closely associated with moderate and severe ID, and are unusual in the general population, the best studied syndrome is that of autism (see chapter 46). A further syndrome is that of stereotypic repetitive movements, such as rocking, head banging, or face slapping. These are most prevalent in those with severe ID, especially when accompanied by sensory deficits (Oliver, Murphy, & Corbett, 1987). These repetitive movements can cause tissue damage, when they are often termed “self-injurious behaviors.” Influences on and Course of Psychopathology High rates of significant psychopathology are present in children with ID by the age of 4 (Baker, Blacher, & Olsson, 2005; Chadwick, Kusel, Cuddy, & Taylor, 2005; Einfeld & Tonge, 1996b; Quine & Pahl, 1989). Two longitudinal cohort studies of mainly untreated young people with ID, the Aberdeen Study (Richardson & Koller, 1996) and the Australian Child to Adult Development (ACAD) Study (Einfeld, Piccinin, Mackinnon et al., 2006; Tonge & Einfeld, 2003) have shown that the severity of overall behavioral and emotional problems declines slowly through to young adulthood but still remains higher than for normally developing young people. The ACAD study found that all psychopathology syndromes declined over 14 years apart from social relating problems, which increased in severity. While the overall severity of psychopathology was similar across the mild to severe range of ID, the type of psychopathology that was most prominent varied. Those with mild ID were more likely to have antisocial and disruptive behaviors, while those with moderate or severe ID had more selfabsorbed and social relating problems. Those with profound ID had lower overall levels of disturbed behavior. The genetic cause of ID had the most influence on severity of psychopathology, and this is largely consistent over time. Assessment of Behavioral and Emotional Disturbance Given that adolescent emotional development continues through the third decade for many young people with ID, child and adolescent mental health professionals are often consulted about young adults with ID. Therefore, the following discussion includes issues pertinent to that age group. The care of children and adolescents with ID often takes place within a matrix of environments, such as home, school, respite care facility, and vocational training placements. It is best to obtain information from as many of these sources as possible. This compensates for the often poor verbal skills of the patient, and enables one to determine if disordered behaviors are limited to one or pervasive through many contexts. As a general guide, the interviewer may use language that would be understood by a child of equivalent mental age. Guided assessment techniques especially with visual cues are also useful, such as a mood thermometer or “COOP” pictograms (Nelson, Wasson, Kirk et al., 1987), and drawing a picture of the family, or the people in his or her group home, if one suspects that these are areas of concern to the patient. This general guide requires several caveats, which derive from the discrepancy that can be present between expressive language, comprehension and emotional maturity. For example, individuals whose ID is a consequence of Williams syndrome may have relatively sophisticated verbal skills that belie a significantly lower level of comprehension and performance skill (Bennett, La Veck, & Sells, 1978). Adolescents with Prader–Willi syndrome often have a more immature level of 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 828

INTELLECTUAL DISABILITY 829 empathy with others’ needs than would be suggested by their level of verbal expression. On the other hand, many young adults or older adolescents with ID reach a level of emotional maturity, perhaps through life experience, which is greater than that suggested by a mental age derived from IQ tests. Such a person might regard an invitation to play with toys as devaluing or demeaning. The interviewer should be aware of a general tendency on the part of some patients to answer “yes” to any question about symptoms. There is some evidence to suggest that this “yeasaying” phenomenon occurs with a higher prevalence in individuals with ID than in the general population (Finlay & Lyons, 2002; Sigelman, Budd, Spankel, & Schoenrock, 1981). Some, although fewer, have the opposite response bias, the “naysaying” response (Sigelman, Schoenrock, Wiver et al., 1979). Given the limitations in applying DSM or ICD diagnoses, formulation is often limited to an assessment of problems operating at the level of symptoms rather than at the level of disorders. A number of questionnaires have been developed with the goal of supporting clinical assessment of children and adolescents with ID. Two in common use are the Aberrant Behavior Checklist (ABC; Aman, Singh, Stewart, & Field, 1985) and the Developmental Behavior Checklist (DBC; Einfeld & Tonge, 2002). The ABC is an informant-based 58-item questionnaire suitable for people with moderate to profound levels of intellectual disability aged 5 and over. The checklist was designed to measure the effects of interventions and levels of maladaptive behavior. The checklist consists of five subscales. The DBC-Parent/Primary Carer and DBC-Teacher versions are 96-item inventories used with young people aged 4–18 years, and measure the Total Behavior Problem Score as well as scores on five subscales: disruptive/antisocial, self-absorbed, communication disturbance, anxiety and social relating. Cases of disorder can be determined by a score of 46 or more on the Total Behavior Problem Score. The instrument is designed to supplement clinician assessment for use in treatment studies. It has been used in epidemiological studies because of the availability of norms from Australia, the UK and the Netherlands. A short form has recently been developed (Taffe, Gray, Einfeld et al., 2007). Issues in the Assessment of Some Particular Psychopathology Syndromes Psychotic disorders are estimated to occur with increased frequency among adults with ID, with a prevalence of about 3–6% (Shedlack, Hennen, Magee, & Cheron, 2005), but the prevalence in children and adolescents is unknown. Despite this, there is evidence that psychosis is overdiagnosed (Aman, 1985). This may derive from the misdiagnosis of hallucinations. For example, care providers often describe a patient as conducting conversations while no-one else is present, or admitting to hearing voices of absent persons. However, if sufficient time is spent questioning and observing the young person, they may explain that they are remembering conversations or just thinking about them. These memories often center on troubling relationships or events and the patient has no difficulty in distinguishing between the remembered conversations and current reality. Such conversations with absent persons may be a behavioral habit, albeit a socially inappropriate one, but they do not constitute hallucinations. Similar caution needs to be exercised in the assessment of possible delusions. A common report is that a young person with ID is unjustifiably complaining that staff or peers are threatening him or her. It should be remembered that young people with ID actually do experience a good deal of devaluation, mockery, rejection and are victims of assaults, so it is not surprising that some individuals develop a sensitivity to communications from others that could be interpreted as critical. A patient interview will often reveal that the individual has not understood what was said and that the “persecutory” ideas resolve with explanation. Where delusions or hallucinations are truly present, the sophistication of their content is appropriate for the mental age. The consequence of uncritical diagnosis of psychotic illness is the overprescription of antipsychotics with serious consequences of impairment of adaptive function, akathisia and long-term risk of tardive dyskinesia. Epilepsy syndromes are frequently associated with behavior disturbances in children and adolescents with ID, especially complex partial seizures and cyclical aggression and epilepsy (see chapter 30). Disinhibition and irritability with clonazepam are common. Given the presence of brain pathology, children and adolescents with ID are susceptible to delirium, and a search should be made for intercurrent physical illness as a cause for a recent onset of behavioral disturbance. Various manifestations of inflexibility in cognitive processing are commonly associated with ID, manifesting as autistic rituals, preoccupations with particular topics, and anxiety with changes in routine or arrangement of objects in the environment. Preoccupations usually are not related to ideas of contamination or harm and lack the “magical” quality of true obsessions. Ascertaining the cause of ID where possible is an important part of assessment, as psychological symptoms can be a consequence of localized or generalized brain pathology. For example, in tuberous sclerosis focal space-occupying lesions or “tubers” are present or develop, often in the limbic system, with consequent production of a wide range of psychiatric symptoms (Roach, 1988). Developmental Issues Key issues presenting to clinicians vary with the mental age of the young person. The birth of a disabled child presents a major crisis for parents. The psychiatrist may be consulted to assist with various aspects of the bereavement process (e.g., parental rejection of the handicapped child, or sudden marital separation). In infancy and childhood, the psychiatrist may be consulted to assist families with manifestations of unresolved grief, such as excessive denial of handicap, as the extent of disability becomes more apparent in the moderately 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 829

CHAPTER 49 830 to severely handicapped. As schooling progresses, the academic handicap of the child with mild ID becomes apparent. Parents of these children must face a grief, which is sometimes more difficult to accept as the cause of handicap is less often identified. Family relationship issues, such as sibling anger consequent to disturbances of family roles, often present in this phase. Autistic and hyperactive symptoms may also lead to psychiatric consultation at this stage. In adolescence, increased size adds to the stress of care of the physically dependent child. Handicapped teenagers with aggressive behaviors may become frightening to mothers or other carers. The emerging sexual drive of teenagers may lead to psychiatric referral for assistance with inappropriate sexual behaviors in both boys and girls. In general, those issues facing the normal adolescent continue through the twenties or thirties for many young people with ID. Psychotic disorders mainly present in early adulthood, but may be earlier in velocardiofacial syndrome and Prader–Willi syndrome. Adaptive decline may appear in this period in individuals with Down syndrome, but manifest dementia is unusual before age 30. Pharmacological Treatment There have been many reports documenting high levels of prescription of psychotropic medications to adults with ID (for a review see Spreat, Conroy, & Fullerton, 2004) but no contemporary surveys for children and adolescents. The surveys of adults with ID have commonly found poor prescribing practice. For example, Holden and Gitelson (2004) found that 37% of people with ID in one Norwegian county were using psychotropics, and that prescriptions frequently violated current guidelines, especially when given by general practitioners. For example, many prescriptions had not been indicated by a diagnosis, alternatives to medications had rarely been explored, and evaluations of effects and side effects were exceptions. Clinical experience suggests that these problems may also apply to children and adolescents with ID. Consequently, it is important for prescribers to consider the use of drugs in children with ID in a systematic way. Such approaches have been described by Einfeld (1990) and Szymanski and King (1999), and are summarized below. Prescribing for children with autism is considered in chapter 46. Mental health professionals are frequently presented with crisis situations, with pressure to prescribe to immediately control disturbed behaviors. However, psychotropic medication will be most beneficial if it follows comprehensive assessment of the individual’s emotional and behavioral disturbance, allowing the formulation of precipitating and ameliorating factors and an assessment of the efficacy of all the past modes of treatment. Where psychotropic medications are urgently required, they should be seen as a short-term intervention to allow full assessment to take place. Proper consideration should be given to the issue of informed consent, particularly with respect to legal requirements (see chapter 8). For most children and adolescents with ID, legal requirements will be the same as for other children, but for older adolescents consent requirements may be different. Frequently, the practitioner is required to make an all-or-none decision with respect to the person’s capacity to consent. In fact, capacity will be quite variable. For example, a person with mild ID may be able to understand that an anxiolytic may make them feel calmer, but not be able to weigh up the risk of longer-term side effects. Fischer (2003) and Clegg (1999) provide useful discussions of consent issues. Pharmacological treatment needs to be an integrated part of other concurrent treatments, and this frequently requires good communication with colleagues providing the other treatments. The precise target symptoms for which the psychotropic medication is being prescribed should be stated. It is very difficult to gain valid information from global impressions, such as “child will be less disruptive” or “more compliant.” It is better to use specific descriptions such as “frequency of child hitting others will be less.” In order to assess this, a method for reliably and validly documenting changes in the target symptoms during the course of treatment is needed. One such method is the Developmental Behavior ChecklistMonitoring module (Einfeld & Tonge, 2002). The use of structured records of behavior is particularly important for children and adolescents with ID, because their care often takes place in a variety of settings (e.g., home, school and respite care). Conflicting information may be received from various carers who attend consultations, each of whom will have a different experience of the patient and different interpretations of behaviors manifested. It is also useful to have two independent carers in a setting (e.g., both parents, or teacher and teacher’s aide) completing such charts independently to provide a basic measure of inter-rater reliability. This record should note whether target symptoms have had a positive response to the medication before the psychotropic medication is continued. It is common for adult patients to be seen who have been receiving large doses of antipsychotics since adolescence without any evidence of benefit. When target symptoms have been reduced or absent for a reasonable period then an attempt should be made to reduce the dosage being prescribed, and structured measures of the effect of this dosage change should be used. Similarly, children and adolescents are frequently maintained on medication long after symptoms have resolved, out of fear that the behaviors will recur, despite developmental or environmental changes. When a psychotropic medication is withdrawn, a proper withdrawal regime should be designed. Withdrawal symptoms appear commonly in individuals with ID if long-standing treatments are terminated suddenly. Because of the presence of organic brain dysfunction, the response to psychotropic drugs is often idiosyncratic. Therefore, the minimum dosage should be used initially with close attention paid to the emergence of side effects. Adverse effects may be more common in individuals with ID, partly because communication difficulties may impede reporting of symptoms (Aman, Paxton, Field, & Foote, 1986). Issues of compliance, pharmacokinetics and drug interactions need consideration also (see chapter 16). 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 830

threshold for instigation of an antidepressant trial is reasonable. SSRIs (see chapter 16) have largely supplanted the tricyclic antidepressants in the treatment of depression in this population, given the lesser impact of side effects. Agitation and nausea are the most common. The evidence that one SSRI has any greater efficacy than another is inconclusive. It is important to start with small doses and for this reason SSRIs that are available in liquid form present advantages in that titration of small doses is possible. SSRIs have also been widely used in the field to treat perseverative and repetitive behaviors including rituals of autism, preoccupations in Asperger’s disorder and self-injurious behavior. Singh, Kleynhans, and Hersen (1998) found marked reductions in self-injurious behavior in 10 out of 12 individuals treated with fluoxetine or fluvoxamine. Janowsky, Shetty, Barnhill, Elamir, and Davis (2005) found statistically significant decreases in the ratings of aggression, self-injurious behavior, destruction/disruption and depression/dysphoria in institutionalized adults. Controlled studies in children and adolescents have not been reported. Anxiolytics There have been no specific studies of the treatment of anxiety in persons with ID. Clinicians have reported improvements in phobic or generalized anxiety disorders as well as obsessivecompulsive disorder with treatment with SSRIs similar to that seen in the general population. Moclobemide is an alternative, but, in the authors’ experience, has less efficacy than the SSRIs. Buspirone has been described in case reports as of assistance. There is little or no indication for the use of benzodiazapines for the treatment of behavioral and emotional disturbance, although they are commonly used in the treatment of epilepsy. Benzodiazapines, particularly clonazepam, frequently cause disinhibition and irritability in persons with organic brain impairments (Kalachnik, Hanzel, Sevenich, & Harder, 2002). When a patient with ID taking benzodiazepines presents with these symptoms, it is always worth asking the patient’s neurologist to consider an alternative anticonvulsant if possible. Mood Stabilizers Typical bipolar illness is occasionally seen, but more frequently people with ID present with instability of mood, that is to say rapid fluctuations between excitement, irritability and high levels of activity alternating with withdrawal and loss of interest. Langee’s (1990) retrospective file study found 42% of individuals treated with lithium for a range of behavior disorders improved significantly. Lithium has also been widely used particularly for impulsive aggressive behavior although evidence for a particular efficacy for this presentation is equivocal. It should be noted that hypothyroidism is common in Down syndrome, so particular care is needed to monitor for the side effects of lithium. Carbamazepine and valproate have been widely used as mood stabilizers in children and adolescents with ID and have lower toxicity risks than lithium. Despite their wide use there are surprisingly few studies of their use, predominantly case reports. Carbamazepine has the INTELLECTUAL DISABILITY 831 Antipsychotics The “typical” antipsychotics (see chapter 16) are the most researched medications in the ID field, but few studies have been rigorous enough to allow conclusions as to their value for the treatment of psychosis or disruptive behavior. The few exceptions have failed to identify any specific impact of antipsychotic medication on the treatment of challenging or problematic behaviors (Brylewski & Duggan, 2004). Aman, De Smedt, Derivan et al. (2002) and Snyder, Turgay, Aman et al. (2002) have reported double-blind placebo controlled trials of risperidone in children and adolescents with ID, using regimens of 0.02–0.06 mg·kg−1 ·day−1 . These studies demonstrated an approximately 50% reduction in conduct disorder symptoms, significantly greater than placebo. Somnolence was transient and there was no impairment of cognition. However, weight gain was common, and prolactin levels were persistently elevated. While these agents cause lower levels of short-term extrapyramidal side effects, there is only limited evidence that the risk of tardive dyskinesia is lessened (Beasley, Dellva, Tamura et al., 1999). There is now substantial evidence that atypical antipsychotics are associated with an increased risk of metabolic syndrome and diabetes (De Hert, van Eyck, & De Nayer, 2006). There is no substantive evidence that the newer antipsychotics have greater efficacy than the traditional ones in individuals with ID. Buzan, Dubovsky, Firestone, and Dal Pozzo (1998) have reviewed 84 published cases of clozapine use in adults with ID. They concluded that clozapine was both efficacious and well tolerated. However, the occasional serious hematological side effects of clozapine warrant caution in using this medication. Antipsychotic medications frequently cause sedation and compromise cognitive functions and self-help skills. In addition, extrapyramidal side effects are common. Tremors and other movement disorders are common in individuals with ID who have taken antipsychotic medication (Sachdev, 1991). Campbell, Armenteros, Malone et al. (1997) found that 34% of autistic children who were receiving haloperidol over a prolonged period developed dyskinesias, mostly associated with withdrawal. Akathisia is an important side effect of antipsychotics to consider in persons with ID. Persons with limited verbal skills frequently are unable to describe the sense of restlessness and irritability, which can be very distressing. This can lead to increased agitation, which may mistakenly be seen as an indication for increased doses of antipsychotics, making the problem worse. Carers are sometimes very surprised to see a decline in agitation or aggression when antipsychotic dose is reduced. Another rare but important complication of antipsychotic medication is neuroleptic malignant syndrome. Boyd (1993; as cited in Reiss & Aman, 1998) found the fatality rate (21%) to be double that occurring in persons without ID. Antidepressants Depression can be difficult to diagnose with confidence in people with limited verbal skills. However, given the relative safety of selective serotonin reuptake inhibitors (SSRIs), a low 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 831

disadvantage of requiring more frequent monitoring of serum level. Stimulants The principal indication is for the same purpose as in children without ID, for the treatment of ADHD. There is some evidence to suggest that those with moderate and severe ID do not respond as well to stimulants as those with mild ID (Aman, Marks, Turbott, Wilsher, & Merry, 1991). ICD-10 includes overactive disorder associated with intellectual disability and stereotyped movements, a category of uncertain validity. Stimulants may worsen epilepsy, anxiety and tics, all of which are more common in children with ID. Curiously, there have been no systematic studies of which this author is aware studying stimulants in Prader–Willi syndrome, despite their appetite suppressant properties. Atomoxetine, a noradrenergic reuptake inhibitor, has been shown in randomized controlled trials to be effective in the treatment of ADHD in children with autism (Arnold, Aman, Cook et al., 2006). Clonidine has been shown in a randomized controlled trial to reduce symptoms in children with ADHD and ID (Agarwal, Sitholey, Kumar, & Prasad, 2001) but at the cost of sedation, tolerance development and requirements to monitor blood pressure. Anticonvulsants Anticonvulsants are frequently prescribed for persons with ID, given the high prevalence of epilepsy. They are also prescribed as mood stabilizers as above. Antilibidinal agents Inappropriate sexual behaviors of some adolescents with ID can cause considerable concern to others and restriction for the individual. Consequently, there has been a growth in the use of testosterone antagonists to reduce libido. Cyproterone is now widely favored as it is active orally, but causes weight gain. Luteinizing hormone-releasing hormone (LHRH) analogs (e.g., leuprorelin) are the most effective and safest method for reducing testosterone levels over prolonged periods but are expensive and of limited availability. The pharmacology of these medications and protocols for their use in paraphilias are described by Reilly, Delva, and Hudson (2000). The pharmacological reduction of libido is potentially of some ethical concern. Prescription to this end should only follow efforts to redirect inappropriate sexual behavior through behavioral and educative means. It may then be that the best interest of the adolescent with ID is served by suppression of a natural aspect of human function. These issues are discussed in greater detail by Clarke (1989). Psychological Treatment There is extensive evidence to support the efficacy of applied behavior analytic approaches in the treatment of problematic or challenging behaviors shown by both children and adults with ID (Ball, Bush, & Emerson, 2004; Emerson, 2001; Lucyshyn, Dunlap, & Albin, 2002; O’Reilly, Sigafoos, Lancioni et al., 2007). While there is significantly less direct evidence, it is likely that some “talking therapies” (e.g., cognitive–behavior therapy) may be efficacious for some children with ID who have acquired more complex language skills (Dagnan, Joahoda, & Kroese, 2007). Detailed guidelines are available with regard to the implementation of behavioral approaches (Ball, Bush, & Emerson, 2004; Bush & Emerson, in press; Luiselli, 2006). Contemporary behavioral approaches (often referred to as positive behavior support) tend to share three key underlying characteristics in that they strive to be functional, constructional and socially valid (Emerson, 2001). A functional approach assumes that it is necessary to identify the specific psychological processes that maintain a person’s challenging behavior in order to maximize the efficacy of interventions. Constructional approaches seek to build competencies, rather than eliminate behaviors. Thus, the key question asked by any constructional intervention is “What should this person be doing in this context (instead of showing challenging behavior)?” rather than “How can we prevent the person engaging in challenging behavior in this context?” Socially valid approaches employ methods that are acceptable to the main constituencies involved to generate socially significant change in the person’s behavior and life opportunities. Behavioral approaches view challenging behavior as an example of operant behavior. That is, challenging behavior is seen as functional and (in a general sense) adaptive. It can be thought of as a way through which the person exercises some degree of control or power over key aspects of their world (see chapter 62). One important aspect of the application of behavioral analytic methods in relation to children with ID is the attention given to the analysis and modification of antecedent and contextual factors. Contextual factors operate in two ways. First, and most importantly, they may establish the motivational base that underlies behavior. Second, they may provide information or cues to the individual concerning the probability of particular behaviors being reinforced. Behavioral Assessment Behavioral assessment has four distinct aims (Emerson, 2005a). These are to: • Identify what it is that the person does that is challenging; • Describe the impact of challenging behavior upon the person’s quality of life; • Attempt to understand the processes underlying the person’s challenging behavior; • Identify possible alternatives to replace challenging behavior. Challenging behaviors are often described by carers and care staff in very general terms. The first step in any process of assessment therefore is to clarify the “How, what, where and when” of challenging behavior. Usually, the information needed to answer these questions will come from interviews with people who are in close contact with the person (e.g., family members, care staff). It may also be useful, both as a CHAPTER 49 832 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 832

prompt during interviewing and as a basis for evaluating change, to use an existing checklist of challenging behavior. If the behavior is very frequent or highly predictable it is also important to spend some time observing the behavior. Describing what the person does that is challenging has two aims. First, it provides a detailed description of the different forms of challenging behavior shown by the person (most people who show challenging behavior do so in several different ways). Second, we need to know about the sequence of behaviors that lead up to an episode of challenging behavior. Challenging behaviors rarely occur “out of the blue.” More commonly, they follow a sequence during which the person’s behavior escalates from more appropriate (e.g., turning away) to less appropriate (e.g., hitting out) ways of attempting to exercise control. Knowledge about sequences can be helpful in: 1 Developing guidelines for managing challenging behavior; and 2 Identifying possible alternatives that could replace challenging behavior. Determining the impact that the person’s challenging behavior has on their life opportunities is important for two reasons. First, it helps prioritize targets for intervention. Second, it provides a basis for evaluating the social validity of future interventions. Practical guidelines for this task are available (Ball, Bush, & Emerson, 2004; Fox & Emerson, 2002). The component of the assessment process that seeks to identify the processes underlying a person’s challenging behavior is commonly referred to as functional assessment. The primary focus of functional assessment is to describe the immediate social and environmental impact of the person’s challenging behavior and in doing so to attempt to identify: 1 Reinforcement contingencies that are maintaining the behavior(s) (see chapter 62); and 2 Setting events or establishing operations that provide the motivational basis for challenging behavior. This descriptive information is often gathered through a combination of structured interview, rating scales and observation (Emerson, 2005a). The aim of constructional interventions is to replace challenging behavior with other (more appropriate) behaviors. The final aim of the assessment process therefore is to identify possible alternatives to challenging behavior. Possible strategies include: 1 Building upon behaviors that already occur earlier in the chain of events leading up to an episode of challenging behavior; 2 Soliciting the views of carers and care staff regarding appropriate alternatives in that particular setting; 3 Undertaking a general assessment of the person’s existing skills and, in particular, their methods of communication. Behavioral Interventions A large array of specific behavioral techniques has been demonstrated to have some degree of efficacy in reducing the rate or severity of challenging behaviors (Ball, Bush, & Emerson, 2004; Emerson, 2001; Lucyshyn, Dunlap, & Albin, 2002; O’Reilly, Sigafoos, Lancioni et al., 2007). The results of a behavioral assessment should identify: 1 Contexts or settings in which challenging behavior is significantly more likely to occur; 2 Establishing operations that may either activate or abolish the contingencies maintaining the person’s challenging behavior. This knowledge opens up possibilities for either preventing or reducing the occurrence of challenging behaviors by the manipulation of antecedent variables. Examples of such approaches include: • Modification of biobehavioral states (e.g., alertness, fatigue, sleep–wake patterns, hormonal changes, drug effects, seizure activity, psychiatric disorders, mood and illness or pain) that are correlated with the occurrence of challenging behavior. • Changing the nature of activities that precede situations in which challenging behavior is more common (e.g., the use of behavioral momentum to increasing compliance and reduce challenging behaviors associated with non-compliance; increasing opportunities for choice making; increasing task variety and physical exercise). • Changing the nature of activities that are concurrent with situations in which challenging behavior is more common through, for example, redesigning curricula to increase preferred activities, generally enriching the person’s environment and providing non-contingent reinforcement and by embedding requests that may elicit challenging behaviors in a more positive prosocial context. Behavioral theory suggests that decreases in challenging behavior may be brought about indirectly through processes of behavioral competition or response covariation. Two sets of procedures that share this common aim are the use of functional displacement and procedures involving the differential reinforcement of other alternative or incompatible behaviors. Intervention through functional displacement (typically referred to as functional communication training) seeks to introduce a new behavior (or increase the rate of a pre-existing behavior) that serves exactly the same function as the person’s challenging behavior. If this alternative is more efficient than the challenging behavior, it should displace the challenging behavior in the person’s behavioral repertoire (Carr, Levin, McConnachie et al., 1994). For example, if a child’s aggression in the classroom serves the function of enabling them to escape from non-preferred activities, teaching the child an alternative method of escape (e.g., verbally requesting a change of activities) will displace aggression as long as it is a more efficient option (i.e., takes less effort and is just as or is more “successful” than aggression in delivering the desired consequences). A number of studies have demonstrated the viability of the procedure across a number of settings, participants and challenging behaviors and have indicated that treatment gains may generalize across settings and therapists and may be maintained over time (Emerson, 2001). A more general set of approaches based on the notion of differential reinforcement also seek to intervene indirectly in challenging behavior by increasing the rate of other behaviors: the differential reinforcement of other behavior (DRO); and INTELLECTUAL DISABILITY 833 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 833

the differential reinforcement of alternative (DRA) or incompatible (DRI) behavior. The available evidence suggests that such procedures may not be particularly effective in reducing severely challenging behaviors (Didden, Duker, & Korzilius, 1997). A third set of procedures seek to intervene by directly changing the contingencies of reinforcement that maintain the person’s challenging behavior. These are primarily based upon variants of extinction (preventing the maintaining contingency from occurring). Whereas extinction may constitute a useful component of an intervention package (e.g., in combination with functional communication training), evidence and consensus suggests it should never form the primary mode of intervention (Ball, Bush, & Emerson, 2004; Emerson, 2001). Finally, there exist a number of “default” or “last resort” approaches based on variations of punishment (including time out), which may be given consideration when more functional and constructional approaches have failed. While they can be effective in temporarily suppressing severe challenging behaviors, their use raises a number of significant ethical issues (Ball, Bush, & Emerson, 2004). In addition to specific treatments, there is also evidence to suggest that programs of family-focused early intervention may have a significant and lasting impact on the cognitive and social development of children with ID (Anderson, Lakin, Hill, & Chen, 1992; Baker & Feinfield, 2007; Guralnick, 2005). This evidence has raised the possibility for the design and delivery of approaches to the prevention of or early intervention for psychopathology among children with ID (Powell, Dunlap, & Fox, 2005). As yet, the effectiveness of such approaches has still to be demonstrated. Mental Health Services for Children and Adolescents with Intellectual Disability Whereas child and adolescent mental health professionals may be well-equipped by training to provide help for children and adolescents with ID, the service settings in which they work have not always welcomed requests to assist such patients. At the same time, carers of those with ID have not always readily sought mental health assistance. In Australia, the USA and other countries, the uncritical application of the normalization principle interpreted mental health interventions as “restrictive” and expressive of the “medical model,” which was seen as devaluing. On the mental health side, the fear grew that, as institutions for people with ID were closed, those with behavioral problems could be “dumped” on the mental health system (Bradley, Summers, Brereton et al., 2007). While this was more apparent in services for adults, child and adolescent mental health services sometimes also reflected this reluctance. As a consequence, families were sometimes told by disability services that their child’s problems were “psychiatric” and needed mental health services, while mental health services told families that the problems were “behavioral” and therefore not the province of mental health. One key dilemma in service design is the extent to which mental health services for children and adolescents with ID should be “mainstreamed” within general child and adolescent mental health systems, or should exist as separate specialized teams. One approach is for generic child and adolescent mental health services to provide initial care, with support available from a specialized resource. In the UK there exist explicit policy objectives to provide comprehensive child and adolescent mental health services in all localities (Department of Health, 2004b) and supposedly to ensure that such services are also responsive to the needs of children and adolescents with ID (BMA Board of Science, 2006; Department of Health, 2004a). Thus, for example, the recent National Service Framework for Children, Young People and Maternity Services states that “All children and young people with both a learning disability and a mental health disorder have access to appropriate child and adolescent mental health services” (Department of Health, 2004b). These policy initiatives reflect a growing understanding of the importance of addressing the mental health needs of children and adolescents more generally (BMA Board of Science, 2006; Department of Health, 2004b), and an appreciation that mental health services for children and adolescents with ID were often of poor quality and highly variable in their availability (Foundation for People with Learning Difficulties, 2003; McCarthy & Boyd, 2002; YoungMinds, 2006). Since the publication of the National Serevice Framework, the percentage of specialist child and adolescent mental health services that also provide support to children and adolescents with ID has risen from 33% to 45% (Barnes, Wistow, Dean et al., 2005). No data are available on the effectiveness or efficiency of these services for children and adolescents with ID. In some service contexts, mental health practitioners may find themselves responsible for ensuring that children and adolescents with ID receive appropriate service for the physical as well as mental health of their patients. Service Issues Across Developmental Phases In the antenatal period, parents may need mental health support in the face of prenatal detection in the fetus of conditions causing ID. The birth of a newborn with obvious congenital abnormalities, especially affecting the brain, precipitates a profound crisis for parents. Child and adolescent mental health professionals are needed either to assist parents with severe difficulty in coping with this crisis, or to support other health professionals who are working with families. The same crisis will be manifest at whatever age ID is first diagnosed. To resolve this crisis, families need to achieve a healthy bereavement in the face of the loss of the wished-for child. Typically, such bereavement recurs as each delayed major developmental milestone is experienced as a loss. During infancy and childhood, the parental focus is often on the acquisition of basic developmental tasks such as mobility, toileting and speech. Despite the evidence described above that behavioral and emotional problems are already apparent in early childhood, parents see these as containable as the child is CHAPTER 49 834 9781405145497_4_049.qxd 29/03/2008 02:54 PM Page 834

still physically small. This can make it difficult to ensure parental interest in early intervention programs to prevent psychopathology. The relationships between the child with ID and their siblings are important for mental health professionals to consider. If the child with ID is older, he or she may become aware over time that his or her younger siblings are granted more independence than he or she is. This reversal of the norm can lead to considerable sibling tension. The normal siblings will often have to contend with the stigma engendered by the presence of their disabled brother or sister. Groups aiming to support siblings of children with ID have been used to address this need (Evans, Jones, & Mansell, 2001). Adolescence is often accompanied by new requests for mental health assistance, frequently on account of the increased size of the child. For example, a large 14-year-old with severe ID whose tantrums are precipitated by the same circumstances as earlier may be difficult to prevent from injuring themselves or others. In young adulthood, individuals with mild ID may still be struggling with adolescent independence and identity issues left behind by their normally developing peers. It is thus appropriate for child and adolescent mental health professionals to continue care for some years into the adult chronological age period. Mental health practitioners will need to interact effectively with a range of other services and these will change with the patient’s development. As the young person with ID grows, the focus of inter-agency collaboration may shift from maternal and infant services, through stages of the preschool and education system, to transitional vocational or day activity programs to degrees of independent living. The state of the young person’s mental health will have a substantial impact on the success of this development. Future Directions Future research and practice hold out the possibility of advances on three fronts: furthering our understanding of the biological bases of ID; strengthening the evidence-base for specific interventions; and developing a more preventative approach to addressing psychopathology in children and adolescents with ID. Prospects for substantial advances in understanding the biology of ID are likely to arise from advances in human genetics. In particular, microarray techniques promise to identify new small aneuploidies underlying ID. Lewis (2005) provides a useful review of these technologies in ID research. We also anticipate continuing advances in mapping gene–behavior pathways in the behavior phenotypes of genetic disorders causing ID (see chapter 24). These advances offer the prospect of prevention through prenatal molecular karyotyping (Larrabee, Johnson, Pestova et al., 2004). The evidence-base relating to interventions for reducing psychopathology primarily addresses issues of efficacy. There is a dearth of evidence relating to effectiveness or the factors associated in successfully scaling up existing interventions, and no evidence relating to efficiency (see chapter 18; Emerson, 2006). Such evidence is a prerequisite for evidence-based policy and practice. The high prevalence and persistence of psychopathology among children and adolescents with ID, when combined with existing knowledge regarding risk factors and possible underlying mechanisms, open up the possibility of developing more preventative approaches. These are likely to encompass a range of possibilities including primary prevention through reducing exposure to risk factors associated with the development of psychopathology (e.g., poverty reduction, enhanced child protection, reduced exposure to unresponsive communicative environments) and developing resilience in the face of exposure to these risk factors, through to increased investment in targeted early intervention. Further Reading Emerson, E., & Einfeld, S. L. (in press). Challenging behaviours: Analysis and intervention in people with intellectual disabilities (3rd ed.). Cambridge: Cambridge University Press. Harris, J. C. (2006). Intellectual disability: Understanding its development, causes, classification, evaluation and treatment. New York: Oxford University Press. References Agarwal, V., Sitholey, P., Kumar, S., & Prasad, M. (2001). Doubleblind, placebo-controlled trial of clonidine in hyperactive children with mental retardation. Mental Retardation, 39, 259–267. Alwan, A., & Modell, B. (2003). Recommendations for introducing genetics services in developing countries. Nature Reviews. Genetics, 4, 61–68. Aman, M. (1991). Assessing psychopathology and behavior problems in persons with mental retardation: A review of available instruments. Rockville, MD: US Department of Health and Human Services. Aman, M. G. (1985). Drugs in mental retardation: treatment or tragedy? Australian and New Zealand Journal of Developmental Disabilities, 10, 215–226. Aman, M. G., De Smedt, G., Derivan, A., Lyons, B., Findling, R. L., & The Risperidone Disruptive Behavior Study Group. (2002). Risperidone treatment of children with disruptive behavior symptoms and subaverage IQ: A double-blind, placebo-controlled study. American Journal of Psychiatry, 159, 1337–1346. Aman, M. G., Marks, R. E., Turbott, S. H., Wilsher, C. P., & Merry, S. N. (1991). Clinical effects of methylphenidate and thioridazine in intellectually subaverage children. 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